Download Practice test for Midterm 1

Practice test for midterm 1
Physics 110
Prof. Guthold
Notes:
- I will provide useful equations on the front page of the test.
- The real test will probably contain about 7 multiple choice questions and four
longer questions where you have to do some calculations, explain the solution to a
problem using physics concepts or explain how a certain physics
demo/experiment works.
- Go over the homework problems as well!
- Go over the examples we did in class!!
- Solutions are at the end of the test.
Part 1. Multiple choice
1.
You are throwing a ball straight up in the air. At the highest point, the ball’s
a. velocity and acceleration are zero.
b. velocity is nonzero but its acceleration is zero.
c. acceleration is nonzero, but its velocity is zero.
d. velocity and acceleration are both nonzero.
2.
You shoot a bullet horizontally with a velocity of 500 m/s, at the exactly the same time as the shoot is
fired you drop a second bullet straight down. The second bullet reaches the ground
a. before the first bullet
b. at the same time as the first bullet
c. after the first bullet
d. before or after, depending on the masses,
e. cannot be determined
You stand on scales on an elevator moving downward at constant velocity. The reading will be
a. less than when stationary.
b. the same as when stationary.
c. more than when stationary.
A car rounds a curve while maintaining a constant speed. Is there a net force on the car as it rounds
the curve?
a. No.
b. Yes.
c. It depends on the sharpness of the curve and the speed of the car.
A battleship simultaneously fires two shells at enemy ships. If the shells follow the parabolic
trajectories shown, which ship gets hit first?
a A.
b. B.
c. Both are hit at the same time.
d need more information.
3.
4.
5.
6.
A locomotive pulls a series of wagons at constant velocity. Which is the correct analysis of the
situation?
a. The train moves forward because the locomotive pulls forward harder on the wagons than the
wagons pull backward on the locomotive.
b. Because there is no net acceleration, thus the net force must be zero. Due to friction, the wagons
pull back as hard on the locomotive as the locomotive is pulling on them.
Practice test for midterm 1
d.
e.
7.
Physics 110
Prof. Guthold
The locomotive’s force on the wagons is as strong as the force of the wagons on the locomotive,
but the frictional force on the locomotive is forward and large while the backward frictional force
on the wagons is small.
The locomotive can pull the wagons forward only if it weighs more than the wagons
A locomotive pulls a series of wagons at constant acceleration. Which is the correct analysis of the
situation?
a. There is a net acceleration, thus the net forward force that the locomotive experiences from the
ground must be larger than the wagons pull backward on the locomotive.
b. Because action always equals reaction, the locomotive cannot pull the wagons the wagons pull
backward just as hard as the locomotive pulls forward, so there is no motion.
d. The locomotive’s force on the wagons is as strong as the force of the wagons on the locomotive,
but the frictional force on the locomotive is forward and large while the backward frictional force
on the wagons is small.
e. The locomotive can pull the wagons forward only if it weighs more than the wagons.
8)
A 12 N book is lifted 4.0 m. The work done by the force lifting the book is
A) 3.0 J
B) 4.0 J
C) 12 J
D) 48 J
9)
A 120-ft long ramp is used to lift a wheeled box to a height of 6.0 ft. Compared to
a direct 6.0-ft lift, the force needed to push the box along the ramp is
A) 20 times as large.
B) unchanged.
C) 1/20 as large.
D) Not enough information is given to determine.
10)
A 120-ft long ramp is used to lift a wheeled box to a height of 6.0 ft. Compared to
a direct 6.0-ft lift, the work performed in pushing the box along the ramp is
A) 20 times as large.
B) unchanged.
C) 1/20 as large.
D) Not enough information is given to determine.
11)
true?
A car is moving forward, and the brakes are applied. Which of the following is
A) The car's velocity is forward, and its acceleration is forward.
B) The car's velocity is forward, and its acceleration is backward.
C) The car's velocity is backward, and its acceleration is forward.
D) The car's velocity is backward, and its acceleration is backward.
Practice test for midterm 1
Physics 110
Prof. Guthold
12)
The net force on a cart is 16 N. The cart accelerates at 8 m/s2. What is the cart's
mass?
A) 128 kg
B) 16 kg
C) 2.0 kg
D) 2.0 pounds
13)
You throw a ball straight up. Ignore air resistance. After it leaves your hand, the
ball will experience
A) only the downward force of its weight, both before and after it reaches its
maximum height.
B) both an upward force, and the downward force of its weight after it rises. The
upward force will gradually diminish to zero at the ball's maximum height, after
which the ball will experience only the
downward force of its weight.
C) an upward force as it rises. This upward force will gradually diminish to zero
at the ball's maximum height, after which the ball will experience only the
downward force of its weight.
D) the upward force of its weight as it rises. Once the ball reaches its maximum
height, it will begin to experience the downward force of its weight.
14)
Your car has a flat tire. You get out the jack, place it under the corner of the car,
and begin to turn the crank that operates the jack. To make the car rise 1 cm, you must
push the jack handle for a distance of 100 cm. Assuming that there is no friction in the
jack and ignoring the weight of the jack itself, the work you do on the jack handle is
A) zero.
B) equal to the work the jack does on the car.
C) more than the work the jack does on the car.
D) less than the work the jack does on the car but more than zero.
15)
The left end of a see-saw accelerates downward, as you view it. By the righthand rule, the torque on the see-saw is
A) away from you.
B) toward you.
C) down.
D) counterclockwise.
Practice test for midterm 1
16)
axis
Physics 110
Prof. Guthold
The moment of inertia of a long thin rod is minimum when it is spinning about an
A) down the center of the rod lengthwise.
B) through the center of the rod, perpendicular to its length.
C) through the end of the rod, perpendicular to its length.
D) The moment of inertia is a constant, so A, B, and C are all equal.
17)
Which is bigger, the peak static or sliding friction?
A) Peak Static
B) Sliding
C) They are equal.
D) The answer depends on the circumstances.
18)
A car increases its speed from 30 mph to 60 mph. What happens to its kinetic
energy?
A) No change
B) It increases by a factor of 2.
C) It increases by a factor of 4.
D) Not enough information is given to determine.
19)
After clearing the bar in the high jump, you land softly on a giant mattress.
Landing on the mattress is much more comfortable than landing on a sand heap of equal
size because
A) you transfer less momentum to the mattress in coming to a stop than you
would have transferred to the sand heap in coming to a stop.
B) the force that the mattress exerts on you to stop your descent is much less than
the force that the sand heap would have exerted on you.
C) you transfer more momentum to the mattress in coming to a stop than you
would have transferred to the sand heap in coming to a stop.
D) your velocity is less as you land on the mattress than it would have been if
you'd landed on the sand heap.
Part 2. Concepts and such
1. In one class demo I pushed Mike in his seat. He claimed that I pushed him and
got upset. I claimed, he was pushing back at me with just the same force. From a
physicist’s point of view, who is right and why? (State the physics law).
Practice test for midterm 1
Physics 110
Prof. Guthold
2. David Thompson, who led NC State to a national championship in basketball in
1974, had a vertical leap of 1.16 meters, greater than Michael Jordan or Vince
Carter. How long could he stay in the air? (Up and down)
3. A car accelerates from rest to 30 m/s in 8 seconds.
a. What is the acceleration?
b. How far did it travel, assuming the acceleration is constant?
4. In the Olympic Winter Games Michele Kwan is doing a beautiful pirouette. You
observe that she starts out with a slow (small angular velocity) spin, but speeds up
rapidly. How does she do it? Use angular momentum and moment of inertia to
explain it.
5. In the Olympics a ski jumper races down from a certain height h and jumps with
an angle of 45º (see diagram). Ignore friction. Energy is conserved. Now consider
the highest point in his flight
a. Does the jumper have a vertical velocity component at this point?
b. Does the jumper have a horizontal velocity component at this point?
c. Does the jumper have kinetic energy at this point?
d. Is his gravitational potential energy more, less or equal to his initial
potential gravitational energy at the beginning of his jump? Explain?
e. Is his total energy more, less or equal to his energy at the beginning of the
jump?
Practice test for midterm 1
Physics 110
Prof. Guthold
Solutions:
1c, 2b, 3b, 4b, since the velocity (direction) is changing, 5b, 6b, 7a, 8d, 9c, 10b, 11b, 12c,
13a, 14b, 15b, 16a, 17a 18c, 19b
Part 2
1.
2.
3.
4.
According to Newton’s 3. law he was pushing back at me with the same force.
20.485= 0.97 s
3.75 m/s2, 120m
She is decreasing her moment of inertia by pulling her arms in and pulling her
mass in towards the axis of rotation as much as possible. Angular momentum is
constant (L = I, thus if I decreases  has to increase by the same factor.
5. a. The jumper has no vertical velocity at the highest point
b. The jumper has a horizontal velocity at the highest point
c. Since the jumper has speed at the highest point he/she also have kinetic
energy (k = ½ mv2).
d. The total energy remains the same. Initially, at the tip of the hill all the
energy was gravitational potential energy. At the highest point in the jump,
the jumper also has kinetic energy, thus the gravitational energy has to be
less than what is was at the top of the hill.
e. Total energy is the same.