CCNY - PHYS 20700 - Fall

Physics 207 Review Questions - I
1m
1. Two ropes are tied to the 2kg ball as shown. At what speed will
the tensions in the ropes be equal? What is the tension at that
speed?
30º
60º
2 kg
2. If you're in a canoe moving at 2 m/s in the positive direction, at what speed
and in what direction would you have to jump out of the canoe in order for it to
stop moving? Your mass is equal to 3/4 the mass of the canoe.
3. A bullet of mass is fired into a block with mass that is at rest. The bullet
becomes embedded in the block, and both objects slide a distance in the
horizontal direction, on a surface with friction. If the friction coefficient is ,
find an expression for the bullet's speed before it hits the block.
4. Kid A is standing on the merry-go-round while Kid B pushes tangentially on
the merry-go-round with a constant force magnitude, resulting in a constant
rotational speed. What is the force that causes kid A to travel in a circle?
A. The force of the push from Kid B
B. The force of gravity
C. The force of static friction
D. The force of kinetic friction
E. The normal force between Kid A and the
platform
5. Based on the same situation as the previous question, in which direction is the
centripetal force acting on Kid A pointed?
A. Down, towards the earth
B. Tangentially, in the same direction as Kid B's push
C. Tangentially, opposite to Kid B's push
D. Towards the center of the merry-go-round
E. Away from the center of the merry-go-round
Physics 207 Review Questions - I
1m
1. Two ropes are tied to the 2kg ball as shown. At what speed will
the tensions in the ropes be equal? What is the tension at that
speed?
30º
60º
2 kg
2. If you're in a canoe moving at 2 m/s in the positive direction, at what speed
and in what direction would you have to jump out of the canoe in order for it to
stop moving? Your mass is equal to 3/4 the mass of the canoe.
3. A bullet of mass is fired into a block with mass that is at rest. The bullet
becomes embedded in the block, and both objects slide a distance in the
horizontal direction, on a surface with friction. If the friction coefficient is ,
find an expression for the bullet's speed before it hits the block.
4. Kid A is standing on the merry-go-round while Kid B pushes tangentially on
the merry-go-round with a constant force magnitude, resulting in a constant
rotational speed. What is the force that causes kid A to travel in a circle?
A. The force of the push from Kid B
B. The force of gravity
C. The force of static friction
D. The force of kinetic friction
E. The normal force between Kid A and the
platform
5. Based on the same situation as the previous question, in which direction is the
centripetal force acting on Kid A pointed?
A. Down, towards the earth
B. Tangentially, in the same direction as Kid B's push
C. Tangentially, opposite to Kid B's push
D. Towards the center of the merry-go-round
E. Away from the center of the merry-go-round
6. A 70 kg human sprinter can accelerate from rest to 10 m/s in 3.0 s. In the
same amount of time, a 30 kg greyhound can go from rest to 20 m/s. What is the
average power output of each?
7. You do 100 J of work while pulling a child back on a swing, whose chain is 2.0
m long, until the swing makes an angle of 30.0° with the vertical. a) What is the
child's mass? (Consider the swing itself and the chain massless) b) Upon releasing
the swing from this position, what will the speed of the child be at the bottom of
the arc?
8. I balance a baseball bat on top of my finger. The center of mass of the bat is
located:
A. at the heavy, thicker end.
B. directly above my finger.
C. under the thin, hand grip part.
D. somewhere not within the volume of the bat.
9. Draw vectors on each image showing the following three situations. Direction
matters most, if you have enough information to say something about the length,
then do so too. (4pts total).
A. The force of friction keeping the coin on the rotating plate.
B. The angular velocity vector, , of the wheel rotating due to the falling
water drops.
C. The various forces (at points A, B, C) acting on the mass as it slides
inside the bowl.
6. A 70 kg human sprinter can accelerate from rest to 10 m/s in 3.0 s. In the
same amount of time, a 30 kg greyhound can go from rest to 20 m/s. What is the
average power output of each?
7. You do 100 J of work while pulling a child back on a swing, whose chain is 2.0
m long, until the swing makes an angle of 30.0° with the vertical. a) What is the
child's mass? (Consider the swing itself and the chain massless) b) Upon releasing
the swing from this position, what will the speed of the child be at the bottom of
the arc?
8. I balance a baseball bat on top of my finger. The center of mass of the bat is
located:
A. at the heavy, thicker end.
B. directly above my finger.
C. under the thin, hand grip part.
D. somewhere not within the volume of the bat.
9. Draw vectors on each image showing the following three situations. Direction
matters most, if you have enough information to say something about the length,
then do so too. (4pts total).
A. The force of friction keeping the coin on the rotating plate.
B. The angular velocity vector, , of the wheel rotating due to the falling
water drops.
C. The various forces (at points A, B, C) acting on the mass as it slides
inside the bowl.