Physics hw/ quiz work and energy

If a spring-operated gun can shoot a pellet to a maximum height of 100 m on Earth, how high could the pellet rise if fired on the moon, where g = 1.6 m/s2?

610 m

A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case. Case A: Thrown straight up Case B: Thrown straight down Case C: Thrown out at an angle of 45 degrees above horizontal. Case D: Thrown straight out horizontally In which case will the speed of the stone be greatest when it hits the water below if there is no significant air resistance?

the speed will be the same in all cases

A person carries a 2 N pebble through the path shown in the figure, starting at point A and ending at point B. The total time from A to B is 6.75 min. How much work did gravity do on the rock between A and B?

-30 J

A 35 N bucket of water is lifted vertically 3 m and then returned to its original position. How much work did gravity do on the bucket during this process?

0 J

A person carries a 25 N rock through the path shown in the figure, starting at point A and ending at point B. The total time from A to B is 1.50 min. How much work did gravity do on the rock between A and B?

0 J

In a ballistics test, a 28-g bullet pierces a sand bag that is 30 cm thick. If the initial bullet velocity was 30 cm and it emerged from the sandbag moving at 30 cm what was the magnitude of the friction force (assuming it to be constant) that the bullet experienced while it traveled through the bag?

130 N

A roller coaster starts from rest at a height h at the left side of a loop-the-loop, as shown in the figure. It is not attached to the track in anyway, and there is no friction from the track or from air resistance. If the radius of the loop is R = 6 m, what is the minimum height h for which the roller coaster will not fall of the track at the top of the loop?

15 m

A 60 kg skier pushes off the top of a frictionless hill with an initial speed of 4.0 m/s. How fast will she be moving after dropping 10 m in elevation? Air resistance is negligible.

15 m/s

A force acts on an object, causing it to move parallel to the force. The graph in the figure shows this force as a function of the position of the object. How much work does the force do as the object moves form 0 m to 4 m?

20 J

A force acts on an object, causing it to move parallel to the force. The graph is the figure shows this force as a function of the position of the object. How much work does the force do as the object moves from 4 m to 6 m?

20 J

An object with a mass of 10 kg is initially at rest at the top of a frictionless inclined plane that rises at 30 degrees above the horizontal. At the top, the object is initially 8 m from the bottom of the incline, as shown in the figure. When the object is released from this position, it eventually stops at a distance d from the bottom of the inclined plane along a horizontal surface, as shown. The coefficient of kinetic friction between the horizontal surface and the object is .2, and air resistance is negligible. Find the distance d.

20 m

The figure shows a famous roller coaster ride. You can ignore friction. If the roller coaster leaves point Q from rest, what is its speed at the top of the 25 m peak (point S)?

22 m/s

When you drop a pebble from height H, it reaches the ground with kinetic energy K if there is no air resistance. From what height should you drop it so it will reach the ground with twice as much kinetic energy?

2H

A 1000 kg car experiences a net force of 9500 N while slowing down from 30 m/s to 15.9 m/s. How far does it travel while slowing down?

34 m

A bead is moving with a speed of 20 m/s at position A on the track shown in the figure. This track is friction-free, and there is no appreciable air resistance. What is the speed of the bead at point C?

34 m/s

In the figure, a ball hangs by a very light string. What is the minimum speed of the ball at the bottom of its swing (point B) in order for it to reach point A, which is 1 m above the bottom of the swing?

4.4 m/s

A traveler pulls on a suitcase strap at an angle 36 degrees above the horizontal. if 555 J of work are done by the strap while moving the suitcase a horizontal distance of 555 J what is the tension in the strap?

46 N

When you drop a pebble from height H, it reaches the ground with speed V if there is no air resistance. From what height should you drop it so it will reach the ground with twice speed?

4H

A 1-kg ball is released from a height of 6 m, and a 2-kg ball is released from a height of 3 m. Air resistance is negligible as they fall. Which of the following statements about these balls are correct?

Both balls will reach the ground with the same kinetic energy && As they reach the ground, the 1 kg ball will be moving faster than the 2 kg ball

Person X pushes twice as hard against a stationary brick wall as person Y. Which one of the following statements is correct?

Both do zero work

A 4.0 kg object is moving with speed 2.0 m/s. A 1.0 kg object is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance before stopping?

Both objects travel the same distance

You and your friend, who weighs the same as you, want to go to the top of the Eiffel Tower. Your friend takes the elevator straight up. You decide to walk up the spiral stairway, taking longer to do so. Compare the gravitational potential energy of you and your friend, after you both reach the top.

Both of you have the same amount of gravitational potential energy at the top

A heavy rock and a light rock are dropped from the same height and experience no significant air resistance as they fall. Which of the following statements about these rocks are correct?

Both rocks have the same speed when they reach the ground && When they reach the ground, the heavier rock has more kinetic energy than the lighter rock

A heavy frog and a light frog jump straight up into the air. They push off in such a way that they both have the same kinetic energy just as they leave the ground. Air resistance is negligible. Which of the following statements about these frogs are correct?

Just as they leave the ground, the lighter frog is moving faster than the heavier frog && Both frogs reach the same maximum height

Three cars (car L, car M, and car N) are moving with the same speed and slam on their brakes. The most massive car is car L, and the least massive is car N. If the tires of all three cars have identical coefficients of kinetic friction with the road surface, for which car is the amount of work done by friction in stopping it the greatest?

car L

A stone is held at a height h above the ground. A second with four times the mass of the first one is held at the same height. The gravitational potential energy of the second stone compared to that of the first stone is

four times as much

Joe and Bill throw identical balls vertically upward. Joe throws his ball with an initial speed twice as high as Bill. If there is no air resistance, the maximum height of Joe's ball will be

four times that of Bill's ball

Two men, Joel and Jerry, push against a car that has stalled, trying unsuccessfully to get it moving. Jerry stops after 10 min, while Joel is able to push for 5 min longer. Compare the work they do on the car.

neither of them does any work

When you throw a pebble straight up with initial speed V, it reaches a maximum height H with no air resistance. At what speed should you throw it up vertically so it will go twice as high?

sqrt2V

Which one has larger kinetic energy: a 500 kg object moving at 40 m/s or a 1000 kg object moving at 20 m/s?

the 500-kg object

Two objects, one of mass m and the other of mass 2m, are dropped from the top of a building. If there is no air resistance, when they hit the ground

the heavier one will have twice the kinetic energy of the lighter one

A stone can slide down one of four different frictionless ramps, as shown in the figure. For which ramp will the speed of the ball be the greatest at the bottom?

the speed of the ball will be the same for all ramps

If the force on an object is in the negative direction, the work it does on the object must be

the work could be either positive of negative, depending on the direction the object moves

You throw a baseball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.

the work is negative on the way up and positive on the way down

A person stands on the edge of a cliff. She throws three identical rocks with the same speed. Rock X is thrown vertically upward, rock Y is thrown horizontally, and rock Z is thrown vertically downward. If the ground at the base of the cliff is level, which rock hits the ground with the greatest speed if there is no air resistance?

they all hit the ground with the same speed

Three cars (car F, car G, and car H) are moving with the same speed and slam on their brakes. The most massive car is car F, and the least massive is car H. If the tires of all three cars have identical coefficients of kinetic friction with the road surface, which car travels the longest distance to skid to a stop?

they all travel the same distance in stopping

A lightweight object and a very heavy object are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hill with no air resistance. Which object rises to a great height?

they both slide to exactly the same height

Swimmers at a water park have a choice of two frictionless water slides, as shown in the figure. Although both slides drop over the same height h, slide 1 is straight while slide 2 is curved, dropping quickly at first and then leveling out. How does the speed v1 of a swimmer reaching the bottom of slide 1 compare with v2, the speed of a swimmer reaching the end of slide 2?

v1= v2