physics chapter6

A baseball (m=145g)traveling 34 m/s moves a fielder's glove backward 24 cm when the ball is caught. What was the average force exerted by the ball on the glove?

Fon glove= 350 N

A satellite in circular orbit around the Earth moves at constant speed. This orbit is maintained by the force of gravity between the Earth and the satellite, yet no work is done on the satellite. How is this possible? No work is done because there is no gravity in space. No work is done if there is no contact between objects. No work is done if objects move in a circle. No work is done if the direction of motion is perpendicular to the force.

No work is done if the direction of motion is perpendicular to the force.

You push very hard on a heavy desk, trying to move it. You do work on the desk: only if it starts moving. whether or not it moves, as long as you are exerting a force. only if it doesn't move. never-it does work on you. None of the above.

Only if it starts moving.

A 975- kg sports car accelerates from rest to 95 km/h in 7.0 s What is the average power delivered by the engine?

P= 4.8×104 W

If the net work done on an object is zero, what can you determine about the object's kinetic energy? The object's kinetic energy is zero. The object's kinetic energy is increasing. The object's kinetic energy remains the same. The object's kinetic energy is decreasing.

The object's kinetic energy remains the same.

Neglecting air resistance, which statement is not true regarding the energy of the ball? The sum of the kinetic energy and potential energy is constant. The potential energy decreases when the ball is coming down. The kinetic energy decreases while the ball is going up. The kinetic energy increases when the ball is coming down. The potential energy decreases while the ball is going up.

The potential energy decreases while the ball is going up.

A car accelerates from rest to 30 km/h. Later, on a highway it accelerates from 30 km/h to 60 km/h Which takes more energy, going from 0 to 30, or from 30 to 60?

30 to 60 km/h

When the speed of your car is doubled, by what factor does its kinetic energy increase? Sqrt2 2 4 8

4

Two objects are moving at equal speed along a level, frictionless surface. The second object has twice the mass of the first object. They both slide up the same frictionless incline plane. Which object rises to a greater height? Object 2 rises to the greater height because it possesses a larger amount of kinetic energy. Object 1 rises to the greater height because it possesses a smaller amount of kinetic energy. Object 1 rises to the greater height because it weighs less. Object 2 rises to the greater height because it contains more mass. The two objects rise to the same height.

The two objects rise to the same height.

A graph depicts force versus position. What represents the work done by the force over the given displacement? the work done is equal to length of the curve. The work done is equal to the area under the curve. The work done is equal to the slope of the curve. The work done is equal to the product of the maximum force times the maximum position. Work cannot be determined from this type of graph.

The work done is equal to the area under the curve.

A 78.0 kg firefighter climbs a flight of stairs 28.0 m high.How much work is required?

W= 2.14×104 J

How much work did the movers do (horizontally) pushing a 47.0-kg crate 10.6 m across a rough floor without acceleration, if the effective coefficient of friction was 0.70?

W= 3400 J

A box of mass 8.0 kg is accelerated from rest across a floor at a rate of 5.0 m/s 2 for 6.0 s Find the net work done on the box.

W= 3600 J

How much work must be done to stop a 1100-kg car traveling at 120 km/h?

W= 6.1×10^5 J

The head of a hammer with a mass of 1.5 kg is allowed to fall onto a nail from a height of 0.60 m What is the maximum amount of work it could do on the nail?

WG= 8.8 J

A ball is thrown straight upward. How does the sign of the work done by gravity while the ball is traveling upward compare with the sign of the work done by gravity while the ball is traveling downward? Work done by gravity is negative while the ball is traveling both upward and downward. Work done by gravity is negative while the ball is traveling upward and positive while the ball is traveling downward. Work done by gravity is positive while the ball is traveling both upward and downward. Work done by gravity is positive while the ball is traveling upward and negative while the ball is traveling downward.

Work done by gravity is negative while the ball is traveling upward and positive while the ball is traveling downward.

A motorcycle drives up a steeply inclined ramp. The work done on the motorcycle by the Earth's gravitational force is ____. negative positive zero

negative

If the speed of a particle is decreased by a factor of three, by what factor does its kinetic energy change?

the kinetic energy is multiplied by a factor = 0.11

During a certain time interval, the net work done on an object is zero joules. We can be certain that ____. the object was at rest during this entire interval the object was at rest at the end of this interval the object's final speed was the same as its initial speed

the object's final speed was the same as its initial speed

Two identical cars are driving in opposite directions at the same speed. Their kinetic energies have ____. different magnitudes and opposite signs the same magnitude, but opposite signs the same magnitude and sign different magnitudes, but the same sign

the same magnitude and sign

If the kinetic energy of a particle is tripled, by what factor has its speed increased?

the speed is multiplied by a factor = 1.7

A sled is initially given a shove up a frictionless 23.0 ∘ incline. It reaches a maximum vertical height 1.05 m higher than where it started at the bottom. What was its initial speed?

v initial= 4.54 m/s

A projectile is fired at an upward angle of 55.0 ∘ from the top of a 120 m cliff with a speed of 195 m/s What will be its speed when it strikes the ground below? (Use conservation of energy and neglect air resistance.)

v strike= 201 m/s

A novice skier, starting from rest, slides down an icy frictionless 12 ∘ incline whose vertical height is 130 m . How fast is she going when she reaches the bottom?

v= 50 m/s

A spring has a spring stiffness constant k of 85.0 N/m How much must this spring be compressed to store 40.0 J of potential energy?

x= 0.970 m

Person B does twice the work of person A, and in one-half of the time . How does the power output of person B compare to person A? Person B has eight times the power output of person A. Person B has four times the power output of person A. Person B has twice the power output of person A. Person B has the same power output as person A. Person B has half the power output of person A.

Person B has four times the power output of person A.