Two objects attract each other with a gravitational force of magnitude 1.01 10-8 N when separated by 19.9 cm. If the total mass of the two objects is 5.11 kg, what is the mass of each?

Answers

Answer 1

Answer:

m₂ = 1.17 kg

Explanation:

Given that,

Force between two objects, [tex]F=1.01\times 10^{-8}\ N[/tex]

Mass of object 1, [tex]m_1=5.11\ kg[/tex]

Distance between masses, r = 19.9 cm = 0.199 m

The gravitational force between two masses is given by :

[tex]F=\dfrac{Gm_1m_2}{r^2}[/tex]

m₂ is the mass of object 2

[tex]m_2=\dfrac{Fr^2}{Gm_1}\\\\m_2=\dfrac{1.01\times 10^{-8}\times (0.199)^2}{6.67\times 10^{-11}\times 5.11}\\\\=1.17\ kg[/tex]

So, the mass of second object is 1.17 kg.


Related Questions

"2.40 A pressure of 4 × 106N/m2 is applied to a body of water that initially filled a 4300 cm3 volume. Estimate its volume after the pressure is applied."

Answers

Answer:Final volume after pressure is applied=4,292cm3

Explanation:

Using the bulk modulus formulae

We have that The bulk modulus of waTer is given as  

K =-V dP/dV

Where  K, the bulk modulus of water = 2.15 x 10^9N/m^2

2.15 x 10^9N/m^2= - 4,300 x  4 × 106N/m2 / dV

dV = - 4,300 x  4 × 10^6N/m^2/ 2.15 x 10^9N/m^2

dV (change in volume)= -8.000cm^3

Final volume after pressure is applied,

V= V+ dV

V= 4300cm3 + (-8.000cm3)

=4300cm3 - 8.000cm3

Final Volume, V =4,292cm3

A baseball is thrown across the field. The ____________is measured from where the ball is thrown to where landed was 75 feet.

motion
direction
distance
reference point

Answers

Answer:

distance i think

Explanation:

2. Which bicyclist was traveling the fastest at the end of the race?

Answers

Answer:

This question is incomplete

Explanation:

This question is incomplete. However, to determine the bicyclist that traveled the fastest at the end of the race, the speed of the bicyclists at the end of the race will determine this (not the bicyclist that came first nor there overall speed). The speed of the bicyclist at the end of the race can be determined by using the formula below

s = d ÷ t

Where s is the speed of each bicyclist at the end of the race

d is the specific distance covered by the bicyclist at the end of the race

t is the time taken for the bicyclist to complete that distance

It should be noted that to get an accurate result, the distance covered at the end of the race must be the same for all the bicyclists.

The x component of vector A is -25.0m and the y component id +40.0m (a) what is the magnitude of A?(b) What is the angle between the direction of A and the positive direction of x?

Answers

Answer:

θ = 122°

Explanation:

Components of a Vector

A vector in the plane can be defined by its rectangular components:

[tex]\vec A =<x,y>[/tex]

Or also can be given by its polar components:

[tex]\vec A =<r,\theta>[/tex]

Where r is the magnitude of the vector and θ is the angle it forms with the positive direction of x.

The relation between them is:

[tex]r=\sqrt{x^2+y^2}[/tex]

[tex]\displaystyle \theta=\arctan\frac{y}{x}[/tex]

It's given the x-component of vector A is x=-25 m and the y-component is y=40 m

(a)

The magnitude of the vector is:

[tex]r=\sqrt{(-25)^2+40^2}[/tex]

[tex]r=\sqrt{625+1600}[/tex]

[tex]r=\sqrt{2225}[/tex]

[tex]r\approx 47.2\ m[/tex]

(b)

[tex]\displaystyle \theta=\arctan\frac{40}{-25}[/tex]

[tex]\displaystyle \theta=\arctan (-1.6)[/tex]

The calculator gives us the value

θ = -58°

But the real angle lies on the second quadrant since x is negative and y is positive, thus:

θ = -58° + 180° = 122°

θ = 122°

A spinning ice skater will slow down if she extends her arms away from her body. Which of the following statements explain this phenomenon
A) circular motion is always uniform
B) A centripetal force always points outward
C) Angular momentum is always conserved
D) Centripetal acceleration cannot change
Marking brainliest

Answers

The answer is B which is a centripetal force always points outwards

Answer:

B, which is why ice skaters often keep their arms close to their body when doing spins and jumps to minimize resistance.

8. A rectangle is measured to be 6.4 +0.2 cm by 8.3 $0.2 cm.

a) Calculate its perimeter in cm

b) Calculate the uncertainty in its perimeter.

Answers

Answer:

a) The perimeter of the rectangle is 29.4 centimeters.

b) The uncertainty in its perimeter is 0.8 centimeters.

Explanation:

a) From Geometry we remember that the perimeter of the rectangle ([tex]p[/tex]), measured in centimeters, is represented by the following formula:

[tex]p = 2\cdot (w+l)[/tex] (1)

Where:

[tex]w[/tex] - Width, measured in centimeters.

[tex]l[/tex] - Length, measured in centimeters.

If we know that [tex]w = 6.4\,cm[/tex] and [tex]l = 8.3\,cm[/tex], then the perimeter of the rectangle is:

[tex]p = 2\cdot (6.4\,cm+8.3\,cm)[/tex]

[tex]p = 29.4\,cm[/tex]

The perimeter of the rectangle is 29.4 centimeters.

b) The uncertainty of the perimeter ([tex]\Delta p[/tex]), measured in centimeters, is estimated by differences. That is:

[tex]\Delta p = 2\cdot (\Delta w + \Delta l)[/tex]  (2)

Where:

[tex]\Delta w[/tex] - Uncertainty in width, measured in centimeters.

[tex]\Delta l[/tex] - Uncertainty in length, measured in centimeters.

If we know that [tex]\Delta w = 0.2\,cm[/tex] and [tex]\Delta l = 0.2\,cm[/tex], then the uncertainty in perimeter is:

[tex]\Delta p = 2\cdot (0.2\,cm+0.2\,cm)[/tex]

[tex]\Delta p = 0.8\,cm[/tex]

The uncertainty in its perimeter is 0.8 centimeters.

A repeated back and forth or up and down motion is called a

Answers

Answer:

A vibration is a repeated back-and-forth or up-and-down motion.

Explanation:

Waves carry energy through empty space or through a medium without transporting matter.

A man walks south at a speed of 2.00 m/s for 60.0 minutes. He then turns around and walks north a distance 3000 m in 25.0 minutes. What is the average velocity of the man during his entire motion?

Answers

Answer:

v = 0.823 m/s

Explanation:

A man walks south at a speed of 2.00 m/s for 60.0 minutes.

The distance covered in South = 60 × 60 × 2 = 7200 m

He then turns around and walks north a distance 3000 m in 25.0 minutes.

As they moved in opposite direction, net displacement will be : 7200 - 3000 = 4200 m

Average velocity of the man = net displacement/time

[tex]v=\dfrac{4200\ m}{(60+25)\times 60}\\\\=0.823\ m/s[/tex]

So, the average velocity of the man is 0.823 m/s.

(b) In the USA, drones are not allowed to be flown too high above the ground.

Suggest one possible risk of flying a drone too high above the ground.




Plz complete thank you in advance

Answers

One possible risk is it could effect planes, radars, weather patterns.

The 400-foot altitude limit was put in place for the sake of airspace safety, and there is a risk to country security as well as the privacy of citizens.

What are drones?

Unmanned aerial vehicles (UAVs), sometimes known as drones, are used for a variety of jobs, from routine to extremely dangerous. These robotic-looking planes can be seen practically everywhere, from delivering groceries to your home to rescuing avalanche victims.

The 400-foot altitude restriction was ultimately implemented for airspace safety. Given the breadth of the airspace above 400 feet, the likelihood of a drone colliding with a human aircraft is exceedingly remote, but the consequences might be disastrous.

Any aerial vehicle that uses software to fly autonomously or that may be controlled remotely by a pilot is referred to as a drone. Numerous drones come equipped with cameras to gather visual data and propellers to stabilize flying paths. Drone technology has been incorporated into industries like videography, search and rescue, agriculture, and transportation.

When in uncontrolled (Class G) airspace, your drone must be flown 400 feet above the ground or less.

To know more about drones:

https://brainly.com/question/27753670

#SPJ2


The earliest mineral observed to showmagnetic properties is called
A leadstone
Blodestone
Cloadstone
Dnone of the above
E all of the above

Answers

Answer:

B: lodestone

Explanation:

Each magnet has its magnetic poles, north (N) and south (S). Diversified ones are attracted and reptiles of the same name are repelled, similarly to charges, so it was considered possible to separate the magnet at the north and south poles.

Magnetic properties can be lost if the magnet is exposed to high temperatures if it falls or due to some mechanical shocks.

A ball is kicked off the ground reaching a maximum height of 60m and lands 80m away. Calculate the initial speed and the angle above the horizontal of the ball when it was kicked​

Answers

Answer:

36.87°

Explanation:

Given

Maximum height = 60m

Horizontal distance (range) = 80,m

Required

Initial speed U

Angle of launch

To get the speed, we will use the range formula;

R = U √2H/g

80 = U√2(60)/9.8

80 = U√12.25

80 = 3.5U

U = 80/3.5

U = 22.86m/s

Get the angle of launch

Using the formula

Theta = tan^-1(y/x)

y is the vertical distance

x is the horizontal distance

Theta = tan^-1(60/80)

Theta = tan^-1(0.75)

Theta = 36.87°

Hence the angle of launch is 36.87°

What is the current in the wire now?

Answers

Answer:

220v

Explanation:

Sorry, the question is incomplete

Answer:

on the potential difference applied and on the resistance of the wire.

Explanation:

Ohms law state that the current through a conductor between two points is directly proportional to the potential difference across the two points. Imtroducing the comstant of proportionality, the resistance, one arrives at the usual athematical equation that describes this relationship: I = V/R.

Please answer my question

Answers

Answer:

Answer is (b) Mercury, venus and Mars.

Explanation:

i think b is correct!!

;-) :-) :-) :-)

during a baseball game you are running home and slide into home plate. However you come up short and you are tagged out. Which force stops you from sliding all the way home? a friction b gravity c pull d push

Answers

Answer:1 because

Explanation: it’s pointing to the earth and gravity

Pulls things down to earth

A model of Earth’s water budget shows that the precipitation on oceans is 420,000 km3 and the precipitation on land is 130,000 km3. If the evaporation from land is 90,000 km3, how much is the evaporation from oceans?

Answers

Answer:

Evaporation from oceans = 460,000 km³

Explanation:

Given:

Precipitation on oceans = 420,000 km³

Precipitation on land = 130,000 km³

Evaporation from land = 90,000 km³

Find:

Evaporation from oceans

Computation:

Evaporation from oceans = Precipitation on oceans + Precipitation on land - Evaporation from land

Evaporation from oceans = 420,000 km³ + 130,000 km³ - 90,000 km³

Evaporation from oceans = 460,000 km³

Answer:ccccccC

Explanation:okay

A large pizza is cut into 8 even slices. A person orders 4 large pizzas from a restaurant. How many total slices of pizza did the person order?

Answers

Answer:

32 slices

Explanation:

Step one:

given data

we are told that 1 large pizza can be cut into 8 even slices

Required

we want to find how many slices are there in 4 large pizzas

Step two:

so if 1 pizza has 8 slices

       4 pizza will have x

cross multiply we have

x= 8*4

x=32 slices

Which city did King David make the royal capital of the Kingdom of Israel?
Canaan
Jerusalem
Philistine
Cairo

Answers

Answer:

Jerusalem

Explanation:

because now a days jerusalem is the royal capital of the kingdom of israel so i conclude that the answer is jerusalem

How much work would be done on a particle with 5.0 C of charge on it if it moved from an equipotential line at 5.5 volts to another equipotential line at 3.5 volts?

Answers

Answer:

10J

Explanation:

In this question we have the following information

The charge of the particle is q = 5 C

The equipotenetial level is V1 = 5.5 v

and also the

equipotenetial level is V2 = 3.5 v

So we calculate the

work done W=q x (v1-v2)

workdone = 5 x (5.5-3.5)

= 5x2

=10 J

Workdone = 10 J

So we conclude that the workdone on a particle with these information is 10j

The atomic of nitrogen is 7. The number of electrons a neutral atom has is_, and its atomic mass is approximately_amu.

Answers

The atomic of nitrogen is 7. The number of electrons a neutral atom has (6) and its atomic mass is approximately (1) amu

PRACTICE
z
1.
What happens to the force of gravity between two objects if the distance between them is doubled?

Answers

Answer:

If the mass of one of the objects is doubled, then the force of gravity between them is doubled. ... Since gravitational force is inversely proportional to the square of the separation distance between the two interacting objects, more separation distance will result in weaker gravitational forces

Explanation:

^^^^yea. What he said lol

During the stretching routine who used the medicine ball for support.

The guy
The guy

The Girl
The Girl

Both people used a ball for support
Both people used a ball for support

No one used it
No one used it

Answers

I used it because I was bored

The cardinal, central, and secondary traits are all part of __________ categorized traits. A. Gordon Allport’s B. Robert McCrae’s C. Paul Costa’s D. Hans Eysenck’s

Answers

Answer:

Gordon Allport’s

Explanation:

edge2o2o

The cardinal, central, and secondary traits are all part of Gordon Allport’s categorized traits. The Correct option is A

Who was Gordon Allport ?

Gordon Willard Allport was born on 11 November 1897 and died 9 October 1967. He was an American psychologist. Allport was first psychologists who studied on personality. he has developed theory of personality. which was one of the greatest finding in the study of personality psychology. He was Appointed  as a social science instructor at Harvard University in 1924,

Gordon Allport was  a great trait theorist who categorized personality traits into three categories cardinal, central, and secondary.

Hence option A is Correct.

To know more about traits, click :

https://brainly.com/question/1463051

#SPJ3

Answer as soon as possible

Answers

Answer:

the velocity of the acorn

Explanation:

just do in in real life and see

Answer:

it is probably the velocity of the acorn

What is the force of gravity for a 12 kg turkey?

Please help asap

Answers

Answer: 117.6N

Explanation:

By the second Newton's law, we know that:

F = m*a

F = force

m = mass

a = acceleration

We know that in the surface of the Earth, the gravitational acceleration is g = 9.8m/s^2.

Then we just can input that acceleration in the above equation, and also replace m by 12kg, and find that the force due the gravity is:

F = 12kg*9.8m/s^2 = 117.6N

why is a mountain ? what is a animal ? what is love ?

Answers

Answer:

When we love someone we experience the same positive thoughts and experiences as when we like a person. But we also experience a deep sense of care and commitment towards that person. Being “in love” includes all the above but also involves feelings of sexual arousal and attraction.

Explanation:

Why evaporation takes place from the Surface?​

Answers

Answer:

in the water cycle evaporation occurs when the sunlight warms the surface of the water the heat from the sun makes the water molecules move faster and faster until they move so fast they can escape as a gas once evaporated a molecule from water that vapor spends about 10 days in the air

premium
A student releases a marble from the top of a ramp. The marble increases speed
while on the ramp then continues across the floor. The marble travels a total of
150cm in 4.80s.
What was the marble's final speed?

Answers

Explanation:

the formula of speed is distance traveled by time it work

Answer:

31.25 cm/sec

__________________________________________________________

Explanation:

We are given:

Distance travelled = 150 cm

Time taken = 4.8 seconds

Final Speed of the Marble:

Speed of the marble = Distance travelled / Time taken

Speed of the marble = 150 / 4.8

Speed of the marble = 31.25 cm/sec

A 4.8-g particle is moving toward a stationary 7.4-g particle at 3.0 m/s. What percentage of the original kinetic energy is convertible to internal energy?

Answers

Answer:

60.185 percent of the original kinetic energy is convertible to internal energy.

Explanation:

Let suppose that collision between both particles is entirely inellastic. If there is no external forces exerted on any of the particles, then we can apply the Principle of Linear Momentum Conservation. That is:

[tex]m_{A}\cdot v_{A,o} + m_{B}\cdot v_{B,o} = (m_{A}+m_{B})\cdot v[/tex]

[tex]v = \frac{m_{A}\cdot v_{A,o}+v_{B}\cdot v_{B,o}}{m_{A}+m_{B}}[/tex] (1)

Where:

[tex]m_{A}[/tex] - Mass of the 4.8-g particle, measured in kilograms.

[tex]m_{B}[/tex] - Mass of the 7.4-g particle, measured in kilograms.

[tex]v_{A,o}[/tex] - Initial speed of the 4.8-g particle, measured in meters per second.

[tex]v_{B,o}[/tex] - Initial speed of the 7.4-g particle, measured in meters per second.

[tex]v[/tex] - Final speed of the collided particles, measured in meters per second.

If we know that [tex]m_{A} = 4.8\times 10^{-3}\,kg[/tex], [tex]m_{B} = 7.4\times 10^{-3}\,kg[/tex], [tex]v_{A,o} = 3\,\frac{m}{s}[/tex] and [tex]v_{B,o} = 0\,\frac{m}{s}[/tex], then the final speed of the system is:

[tex]v = \frac{(4.8\times 10^{-3}\,kg)\cdot \left(3\,\frac{m}{s} \right)+(7.4\times 10^{-3}\,kg)\cdot \left(0\,\frac{m}{s} \right)}{4.8\times 10^{-3}\,kg+7.4\times 10^{-3}\,kg}[/tex]

[tex]v = 1.180\,\frac{m}{s}[/tex]

During the collision part of the initial energy is dissipated in the form of heat, which is related to the internal energy ([tex]\Delta U[/tex]), measured in joules. According to the Principle of Energy Conservation, we have the following model:

[tex]\Delta U = K_{A}+K_{B}-K[/tex] (2)

Where:

[tex]K_{A}[/tex], [tex]K_{B}[/tex] - Initial translational kinetic energies of each particle, measured in joules.

[tex]K[/tex] - Final translational kinetic energy of the collided particles, measured in joules.

By applying the definition of translational kinetic energy, we expand and simplify the equation above:

[tex]\Delta U = \frac{1}{2}\cdot m_{A}\cdot v_{A,o}^{2}+\frac{1}{2}\cdot m_{B}\cdot v_{B,o}^{2} -\frac{1}{2}\cdot (m_{A}+m_{B})\cdot v^{2}[/tex] (3)

If we get that  [tex]m_{A} = 4.8\times 10^{-3}\,kg[/tex], [tex]m_{B} = 7.4\times 10^{-3}\,kg[/tex], [tex]v_{A,o} = 3\,\frac{m}{s}[/tex], [tex]v_{B,o} = 0\,\frac{m}{s}[/tex] and [tex]v = 1.180\,\frac{m}{s}[/tex], the internal energy associated with the system is:

[tex]\Delta U = \frac{1}{2}\cdot (4.8\times 10^{-3}\,kg)\cdot \left(3\,\frac{m}{s} \right)^{2}+ \frac{1}{2}\cdot (7.4\times 10^{-3}\,kg)\cdot \left(0\,\frac{m}{s} \right)^{2}-\frac{1}{2}\cdot (4.8\times 10^{-3}\,kg+7.4\times 10^{-3}\,kg)\cdot \left(1.180\,\frac{m}{s} \right)^{2}[/tex]

[tex]\Delta U = 0.013\,J[/tex]

And the initial energy of both particles is:

[tex]E_{o} = \frac{1}{2}\cdot (4.8\times 10^{-3}\,kg)\cdot \left(3\,\frac{m}{s}\right)^{2}+\frac{1}{2}\cdot (7.4\times 10^{-3}\,kg)\cdot \left(0\,\frac{m}{s} \right)^{2}[/tex]

[tex]E_{o} = 0.0216\,J[/tex]

Lastly, the percentage of the original kinetic energy that is convertible to internal energy is: ([tex]\Delta U = 0.013\,J[/tex], [tex]E_{o} = 0.0216\,J[/tex])

[tex]\%e = \frac{\Delta U}{E_{o}}\times 100\,\%[/tex] (4)

[tex]\%e = \frac{0.013\,J}{0.0216\,J}\times 100\,\%[/tex]

[tex]\%e = 60.185\,\%[/tex]

60.185 percent of the original kinetic energy is convertible to internal energy.

Bob rides his bike with a constant speed of 10 miles per hour. How long will he take to travel a distance of 15 miles?

Answers

[tex]{\underline{\pink{\textsf{\textbf{ Answer : }}}}}[/tex]

➡ 150hrs.

[tex]{\underline{\pink{\textsf{\textbf{Explanation : }}}}}[/tex]

➡ Time = distance × speed

➡ Time = 15*10

➡ Time = 150hrs ans.

While riding a multispeed bicycle, the rider can select the radius of the rear sprocket that is fixed to the rear axle. The front sprocket of a bicycle has radius 12.0 cm. If the angular speed of the front sprocket is 0.600 rev/s, what is the radius of the rear sprocket for which the tangential speed of a point on the rim of the rear wheel will be 5.00 m/s?

Answers

Answer:

2.9 cm

Explanation:

Assuming that the rear wheel has a radius of 0.330 m

Given that

r(a) = 12 cm -> 0.12 m

w(a) = 0.6 rev/s -> 3.77 rad/s

v = 5 m/s

r(w) = 0.330 m

The speed on any point on the rim at the sprocket in the front is

v(a) = w(a).r(a) = 3.77 * 0.12 = 0.4524 m/s

Also,

v(a) = speed at any point on the chain

v(b) = speed at any point on the rim of the rear sprocket

v(a) = v(b)

where v(b) = w(b).r(b)

Recall that the speed at any point on the rear wheel is v, where

v = w(b).r(w)

5 = w(b) * 0.330

w(b) = 5/0.330

w(b) = 15.15 rad/s

On substituting this in the equation, we have

v(b) = w(b).r(b).

Remember also, that v(a) = v(b), so

0.4524 = 15.15 * r(b)

r(b) = 0.4524 / 15.15

r(b) = 0.029 m -> 2.9 cm

Therefore, the radius of the rear sprocket needed is 2.9 cm

Other Questions
Answer as soon as possible X^2 + 10x = 0How do I solve for a completed square ? 1377. Thence the welter of waters washes up 1378. Wan to welkin when winds bestir 1379. Evil storms, and air grows dusk, 1380. And the heavens weep. Now is help once more 1381. With thee alone! The land thou knowst not, 1382. Place of fear, where thou findest out 1383. That sin-flecked being. Seek if thou dare! Is best descibed as active,evil,unbelieable, and damp can someone please help me;/Which made Atlanta an important city for the Confederacy? Check all that apply.It was located on the Mississippi.It was located near the Union states.It was a communications center.It was a transportation hub.It was a manufacturing center.It was a center of learning. in 2011 there were 3223 sea otters in Monterey Bay California the bay is approximately 77 mi. to the nearest whole number what was the density of the sea otter population PEOPLE SHOW ANSWERS PLEASE AND WILL GIVE BRAINLIEST 8. The ratio of cats to dogs at a pet showis 1:3.a) What percent of the pets at theshow are cats? How does Hamilton respond to Jefferson at the first cabinet meeting? What does Alexander decide to do when Angelica comes home and goes upstate with Eliza? What does Hamilton do after Maria Reynolds husband finds out about their affair? I need help pleaseeee "nepali arts are related to religious and cultural practices" justify the statement. A hungry Emperor penguin was swimming 21 feet below sea level. It swam up 9 feet to eat a fish. What is the position of the penguin now relative to sea level? Which statement correctly describes the reason for the high specific heat of water?A.) Water has unusually strong hydrogen bonding. These bonds require extra energy to break. Therefore, water has a high specific heat.B.) The oxygen and hydrogen atoms in water molecules are bonded together with strong covalent bonds. The bonds require extra energy to break. Therefore, water has a high specific heat.C.) Water is made of ions. The attraction between ions requires extra energy to break. Therefore, water has a high specific heat.D.) The oxygen and hydrogen atoms in water molecules are bonded together with strong ionic bonds. The bonds require extra energy to break. Therefore, water has a high specific heat. can someone please help me Evaluate 1/6t+1/12 when t=1/2 Carefully study the chart above. If the trends seen on this chart continue, future literacy rates would___________?A. Literacy rates would stay about the same.B. Literacy rates would continue to increase, and the gap between men and women would continue to decrease.C. Literacy rates would continue to increase, and the gap between men and women would stay the same.D. Literacy rates would continue to decreasePlease select the best answer from the choices provided A B C D Find the point that is a solution for y=6x+8 If your nominal rate of return is 14.38 percent and your real rate of return is 4.97 percent, what is the inflation rate write 6.085 in word form 20 POINTSNEED HELP ASAP If f(x) = 3x-2 and g(x) = 2x+1, find (f+g)(x)A. x-3B. x-1C. 5x-1D. 5x-3 What is the sum of two consecutive numbers is 141 You can expect to see ________. A. STOP signs or traffic lights on limited access highways B. only traffic lights on limited access highways C. only STOP signs on limited access highways D. no STOP signs or traffic lights on limited access highways