PHYS 110 Exam 2 CH 4-7

A 60-kg person on a merry-go-round is traveling in a circle with a radius of 3 m at a speed of 3 m/s. What is the magnitude of the acceleration experienced by this person?

3 m/s2

Kinetic energy is defined to be one-half the

mass times the speed squared.

Linear momentum is defined to be

mass times velocity.

An 90-kg satellite orbits a distant planet with a radius of 4000 km and a period of 280 min. From the radius and period, you calculate the satellite's acceleration to be 0.56 m/s2. What is the gravitational force on the satellite?

50.4 N

Carmen is standing on a giant skateboard that is initially at rest. If we ignore frictional effects with the floor, what is the momentum of the skateboard if Carmon walks to the right with a momentum of 500 kg·m/s?

500 kg·m/s to the left

An object has a velocity toward the south. If a force directed toward the north acts on the object, it will initially cause the kinetic energy of the object to ____.

decrease

Over which of the following locations is it possible to have a synchronous satellite?

equator

Which of the following objects has the largest kinetic energy? A mass of ____ with a speed of ____.

6 kg ... 3 m/s

Juan has a mass of 60 kg and is standing on a giant skateboard that is initially at rest and has a mass of 30 kg. If we ignore frictional effects with the floor, what is the speed of the skateboard if Juan walks to the right with a speed of 3 m/s?

6 m/s

A 3-kg mass is released at the top of a frictionless slide that is 2 m high. What is the kinetic energy of the mass when it reaches the bottom?

60 J

A 3-kg toy car with a speed of 6 m/s collides head-on with a 2-kg car traveling in the opposite direction with a speed of 4 m/s. If the cars are locked together after the collision with a speed of 2 m/s, how much kinetic energy is lost?

60 J

Your instructor rides on a merry-go-round turning at a constant rate. In which direction does the net force on your instructor point?

toward the center

A man with a mass of 70 kg falls 10 m. How much gravitational potential energy does he lose?

7000 J

A man with a mass of 70 kg falls 10 m. How much kinetic energy does he gain?

7000 J

Earth exerts a gravitational force of 7000 N on one of the communications satellites. What force does the satellite exert on Earth?

7000 N

A car drives off a vertical cliff at a speed of 24 m/s. If it takes 3 s for the car to hit the ground, how far from the base of the cliff does it land?

72 m

What is the impulse of a 5 N force acting for 15 s?

75 N·s

What centripetal acceleration is required to follow a circular path with a radius of 50 m at a speed of 20 m/s?

8 m/s2

What change in momentum occurs when a force of 20 N acts for 4 s?

80 kg·m/s

The acceleration due to gravity on Titan, Saturn's largest Moon, is about 1.4 m/s2. What would a 60-kg scientific instrument weigh on Titan?

84 N

Which of the following statements about projectile motion is true?

All of the above statements are true.

We can explain the recoil that occurs when a rifle is fired by using

Any of the above.

A car moves with constant speed in the clockwise direction around the test track shown in the top view diagram below left. Use the arrows shown below right to answer the following questions. A car moves with constant speed in the clockwise direction around the test track shown in the top view diagram below left. Use the arrows shown below right to answer the following questions.

Arrow 5

A car moves with constant speed in the clockwise direction around the test track shown in the top view diagram below left. Use the arrows shown below right to answer the following questions. Refer to Exhibit 4-3. Which arrow best represents the direction of the net force exerted on the car when it is located at point B?

Arrow 7

A car moves with constant speed in the clockwise direction around the test track shown in the top view diagram below left. Use the arrows shown below right to answer the following questions. Refer to Exhibit 4-3.Which arrow best represents the direction of the car's acceleration when it is located at point C?

Arrow 8

Two objects have different masses but the same kinetic energies. If you stop them with the same retarding force, which one will stop in the shorter distance?

Both stop in the same distance.

On the surface of a certain planet, the acceleration due to gravity f has numerical value 5.2m/s^2. This means that

The weight of a 1 kg of a body at that location is 5.2N

Does the Moon orbit the Sun?

Yes, but it also orbits Earth.

If a race car is traveling around a circular track at a constant speed of 100 mph, we know that the car experiences

a centripetal force.

Which of the following is NOT a unit of energy?

watt

The kinetic energy of an object moving in a circle at a constant speed is

constant.

A 2-kg ball traveling to the right with a speed of 4 m/s collides with a 4-kg ball traveling to the left with a speed of 2 m/s. The total momentum of the two balls after the collision is

zero

A 3-kg ball traveling to the right with a speed of 4 m/s collides with a 4-kg ball traveling to the left with a speed of 3 m/s. What is the total momentum of the two balls before and after the collision?

zero

A racecar is moving counterclockwise on a circular path as shown in the diagram. Imagine that at this instant, the car is at point P and moving at a speed of 100 mph. Refer to Exhibit 4-1. In what direction does the acceleration point?

←

A racecar is moving counterclockwise on a circular path as shown in the diagram. Imagine that at this instant, the car is at point P and moving at a speed of 100 mph. Refer to Exhibit 4-1. In what direction does the net force point?

←

A racecar is moving counterclockwise on a circular path as shown in the diagram. Imagine that at this instant, the car is at point P and moving at a speed of 100 mph. Refer to Exhibit 4-1. In what direction does the velocity vector point?

↑

A ball dropped from a height of 10 m only bounces to a height of 5 m. Which of the following statements is valid for this situation?

None of the above.

A 0.5-kg air-hockey puck is initially at rest. What will its kinetic energy be after a net force of 0.6 N acts on it for a distance of 2 m?

1.2 J

A father (m = 90 kg) and son (m = 45 kg) are standing facing each other on a frozen pond. The son pushes on the father and finds himself moving backward at 3 m/s after they have separated. How fast is the father moving?

1.5 m/s

It takes about 30 s for a jet plane to go from rest to the takeoff speed of 100 mph (44.7 m/s). What is the average horizontal force that the seat exerts on the back of a 80-kg passenger during takeoff?

119 N

A 320-kg satellite experiences a gravitational force of 800 N. What is the radius of the satellite's orbit? (Earth's radius is 6,400 km.)

12,800 km

A tennis ball (m = 0.2 kg) is thrown at a brick wall. It is traveling horizontally at 16 m/s just before hitting the wall and rebounds from the wall at 8 m/s, still traveling horizontally. The ball is in contact with the wall for 0.04 s. What is the magnitude of the average force of the wall on the ball?

120 N

Angel Falls in southeastern Venezuela is the highest uninterrupted waterfall in the world, dropping 979 m (3212 ft). Ignoring air resistance, it would take 14 s for the water to fall from the lip of the falls to the river below. If the water lands 50 m from the base of the vertical cliff, what was its horizontal speed at the top?

3.6 m/s

What is the kinetic energy of an 80-kg sprinter running at 9 m/s?

3240 J

If a sports car with a mass of 1000 kg travels down the road with a speed of 40 m/s, its momentum is

40,000 kg·m/s

The gravitational force between two metal spheres in outer space is 1000 N. How large would this force be if each of the two spheres had twice the mass?

4000 N

How much work does a 60-kg person do against gravity in walking up a trail that gains 720 m in elevation?

432,000 J

If a sports car with a mass of 1000 kg travels down the road with a speed of 30 m/s, its kinetic energy is

450,000 J.

What average net force is needed to accelerate a 1200-kg car to a speed of 30 m/s in a time of 8 s?

4500 N

Which of the following will cause the largest change in the momentum of an object? A force of ____ acting for ____.

5 N ... 5 s

On the surface of a certain planet, the gravitational field strength has numerical value gplanet. An object that experiences a gravitational force of 0.7 newtons on this planet must have a mass of

0.7/gplanet

A rock is thrown off a tall cliff with a vertical speed of 25 m/s upward and a horizontal speed of 30 m/s. What will these speeds be 3 s later?

5 m/s downward and 30 m/s horizontal

A 600-kg geosynchronous satellite has an orbital radius of 6.6 Earth radii. What gravitational force does Earth exert on the satellite?

138 N

Sally is an astronaut who has a mass of 60 kg. Currently she is conducting experiments in a permanent space station that is orbiting Earth at an altitude equal to Earth's radius. Refer to Exhibit 5-1. What is the force of gravity acting on Sally while she is in the space station?

150 N

A baseball is hit with a vertical speed of 10 m/s and a horizontal speed of 30 m/s. How long will the ball remain in the air?

2 s

What is the acceleration due to Earth's gravity at a distance of one Earth radius above Earth's surface?

2.5 m/s2

Communications satellites are synchronous satellites that orbit Earth each

24 hours

What impulse is need to stop a 1200-kg car traveling at 20 m/s?

24,000 N·s

A rock is thrown off a tall cliff with a vertical speed of 25 m/s upward and a horizontal speed of 30 m/s. If the rock lands 8 s later, how far from the base of the cliff will it land?

240 m

What average force is required to stop a 120-kg football player running at 8 m/s in a time of 0.4 s?

2400 N

A 1400-kg car has a speed of 20 m/s. What average force is required to stop the car in 10 s?

2800 N

What happens to the total momentum of a star that undergoes a supernova explosion?

It remains constant.

A 2-kg ball is thrown horizontally at a speed of 10 m/s. At the same time a 1-kg ball is dropped from the same height. Ignoring air resistance, which ball hits the ground first?

It's a tie.

Assuming that your author jumps off the roof of a garage and lands on the ground, how will the impulse the ground exerts on him if he lands on grass compare to that if he lands on concrete?

The impulses will be the same independent of the surface.

If Earth's mass were suddenly and magically reduced to half its present value, the Sun's gravitational force on Earth would

be reduced by a factor of 2.

Air bags are used by stunt people when they fall off buildings to reduce the ____ that occurs during the collision.

force

Assume that two cars have the same mass, but that the red car has twice the speed of the blue car. We then know that the red car has ____ kinetic energy as the blue car.

four times as much

Padded dashboards in automobiles are safer because the

impact time is greater

A system consisting of two particles has zero kinetic energy. The momentum of this system

is definitely zero

If a sports car with a mass of 1000 kg travels down the road with a speed of 30 m/s, its momentum is 30,000

kg·m/s

Which of the following is an energy unit?

kilowatt-hour

Which has the greater kinetic energy, a heavy truck at rest or a moving roller skate?

the roller skate

Which has the greater momentum, a heavy truck at rest or a moving roller skate?

the roller skate

The gravitational attraction of the Sun for Earth is ____ that of Earth for the Sun.

the same as