Ch 6 and 7 homework
Why does the bowling ball behave the way it does the first time Dr. Hewitt lifts the bowling ball near his teeth and lets go? Some of the initial energy of the ball was lost, and it had less energy than it had at the beginning. All of the initial energy of the ball was lost when the ball was released. All of the initial energy of the ball was converted completely back to potential energy when the ball returned.
All of the initial energy of the ball was converted completely back to potential energy when the ball returned.
Which requires more work--lifting a 50-kg sack vertically 2 m or lifting a 25-kg sack vertically 4 m? The 25-kg sack requires more work. The sack lifted 4 m requires more work. The 50-kg sack requires more work. Both take the same 1000 J.
Both take the same 1000 J.
In what way does the impulse-momentum relationship relate to Newton's second law? F=ma=mΔv/Δt, so Ft=Δ(mv) F=ma=mΔvΔt, so F/t=Δ(mv) F=ma=mΔv/Δt, so F=Δ(mv) F=ma=mΔv/Δt, so Ft=Δ(mv)t
F=ma=mΔv/Δt, so Ft=Δ(mv)
If it were raised twice as high, how much more potential energy would it have? It would have equal and opposite potential energy. It would have half as much potential energy. It would have the exact same potential energy. It would have twice as much potential energy.
It would have twice as much potential energy.
In which type or kind of collision is momentum conserved: elastic or inelastic? Momentum is conserved in elastic and inelastic collisions. Momentum is conserved only in elastic collisions. Momentum is conserved only in inelastic collisions. Momentum is conserved in neither elastic nor inelastic collisions.
Momentum is conserved in elastic and inelastic collisions.
What happens the second time Dr. Hewitt lifts the bowling ball near his teeth and gives it a push? The ball leaves Dr. Hewitt and returns to him, stopping short of the point where it was released. The ball returns to Dr. Hewitt, stopping almost exactly at the point where it was released. The ball leaves Dr. Hewitt and returns to him, going past the point where it was released.
The ball leaves Dr. Hewitt and returns to him, going past the point where it was released.
What happens the first time Dr. Hewitt lifts the bowling ball near his teeth and lets go? The ball returns to Dr. Hewitt, stopping almost exactly at the point where it was released. The ball leaves Dr. Hewitt and returns to him, stopping short of the point where it was released. The ball leaves Dr. Hewitt and returns to him, going past the point where it was released.
The ball returns to Dr. Hewitt, stopping almost exactly at the point where it was released.
Why does the bowling ball behave as it does when Dr. Hewitt lifts it and gives it a push? The ball's initial energy is lost. The extra energy from the push is converted into kinetic energy, which is then converted into more potential energy at the end of the motion than the ball had when it was released. The ball gains potential energy after it is released.
The extra energy from the push is converted into kinetic energy, which is then converted into more potential energy at the end of the motion than the ball had when it was released.
Why does a long cannon impart more speed to a cannonball than a small cannon for the same force? The force is applied for a longer time in the short cannon. The force per unit time is greater for a long cannon. The force is applied for a shorter time in the long cannon. The force is applied for a longer time in the long cannon.
The force is applied for a longer time in the long cannon.
Which has a greater momentum, a heavy truck at rest or a mouse running along the street? Both have the same momentum. Both have zero momentum. The heavy truck at rest. The running mouse.
The running mouse.
How does the speed of car B compare with the initial speed of car A? The speed of car B is twice the initial speed of car A. The speed of car B is zero. The speed of car B is equal to the initial speed of car A. The speed of car B is half the initial speed of car A.
The speed of car B is equal to the initial speed of car A.
Predict what will happen if you reduce the magnitude of the velocity of the green truck to a magnitude smaller than that of the red truck. The trucks will stick together after the collision and move to the right. The trucks will stick together after the collision and not move. The trucks will stick together after the collision and move to the left.
The trucks will stick together after the collision and move to the left.
Click "Reset." Now, predict what will happen if you change the velocity of the red truck so that it has a magnitude smaller than that of the green truck but is negative. The trucks will stick together after the collision and move to the right. The trucks will stick together after the collision and not move. The trucks will stick together after the collision and move to the left.
The trucks will stick together after the collision and move to the right.
Click "Reset." Now, predict what will happen if you change the velocity of the red truck so that it has a magnitude smaller than that of the green truck but is positive. The trucks will stick together after the collision and move to the right. The trucks will stick together after the collision and not move. The trucks will stick together after the collision and move to the left.
The trucks will stick together after the collision and move to the right.
Click "Reset." Now, predict what will happen if you increase the mass of the green truck so that it is greater than the mass of the red truck. The trucks will stick together after the collision and move to the right. The trucks will stick together after the collision and not move. The trucks will stick together after the collision and move to the left.
The trucks will stick together after the collision and move to the right.
Before you click "Play," predict what will happen if the red and green truck with equal mass and equal magnitude of velocity collide. The trucks will stick together after the collision and not move. The trucks will stick together after the collision and move to the left. The trucks will stick together after the collision and move to the right.
The trucks will stick together after the collision and not move.
Suppose we replace both hover pucks with pucks that are the same size as the originals but twice as massive. Otherwise, we keep the experiment the same. Compared to the pucks in the video, this pair of pucks will rotate at the same rate. one-fourth as fast. four times as fast. one-half as fast. twice as fast.
at the same rate.
When traveling twice as fast your kinetic energy is increased _______. by four times by three times not at all by two times
by four times
Energy cannot be _______. destroyed transferred transformed transferred, transformed, or destroyed
destroyed
When a cannonball is fired from a cannon, the momentum of the recoiling cannon is momentarily _______. the same as that of the fired cannonball equal and opposite to the momentum of the fired cannonball less than the momentum of the fired cannonball greater than the momentum of the fired cannonball
equal and opposite to the momentum of the fired cannonball
The work that is done when twice the load is lifted twice the distance is _______. four times as much three times as much the same twice as much
four times as much
The amount of kinetic energy an object has depends on its mass and its speed. Rank the following sets of oranges and cantaloupes from least kinetic energy to greatest kinetic energy. If two sets have the same amount of kinetic energy, place one on top of the other. (1) mass: m and speed: v; (2) total mass: 2 m and speed: 1/2 v; (3) mass: 4 m and speed: 1/4 v; (4) total mass: 4 m and speed: v; (5) mass: 4 m and speed: v
least KN: 3, 2, 1, 4 and 5 most KN is NOT RIGHT
A motorcycle drives up a steeply inclined ramp. The work done on the motorcycle by the Earth's gravitational force is ____. positive zero negative
negative
When a big fish swims into an oncoming smaller fish and swallows it, the momentum of the two-fish system _______. remains the same Decreases Increases converts to spurious motion
remains the same
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 at the end of this interval the object's final speed was the same as its initial speed the object was at rest during this entire interval
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, but the same sign the same magnitude and sign different magnitudes and opposite signs the same magnitude, but opposite signs
the same magnitude and sign
