Fall 2002 Physics 101 Hour Exam 2
(25 questions)

The grading button and a description of the scoring criteria are at the bottom of this page. Basic questions are marked by a single star *. More difficult questions are marked by two stars **. The most challenging questions are marked by three stars ***.

This exam consists of 25 questions; true-false questions are worth 2 points each, three-choice multiple choice questions are worth 3 points each, five-choice multiple choice questions are worth 6 points each. The maximum possible score is 125. When the exam was given, the mean was 95.9; the median was 99. Click here to see the formula sheet that came with the exam.


QUESTION 1*

A crane lifts a load at constant speed up 5 m. doing 12,000 J work. What is the mass of the load?

(a)   138 kg
(b)   206 kg
(c)   245 kg
(d)   312 kg
(e)   323 kg


QUESTION 2**

Two blocks, one of mass M and the other of mass 2M, are on a horizontal frictionless surface and are initially at rest. Then each block is acted up by the same constant force F for the same time interval. Which block has the larger kinetic energy?

(a)   the block of mass M
(b)   the block of mass 2M
(c)   The two blocks have the same kinetic energy.


QUESTION 3*

A block is moved 2.5 meters across a floor by two forces. The force F1 = 20 N pushes at an angle of 45o below the horizontal and the force F2 = 10 N pulls horizontally. Compare the work done by the two forces.

(a)   W1 < W2
(b)   W1 = W2
(c)   W1 > W2


QUESTION 4**

A rocket is moving at a speed V0 and suddenly breaks into two pieces of equal mass. They fly off with velocities V1 and V2, as shown in the drawing below. Which of the following equations describes the relation between the magnitude of V1 and V2?

(a)   V1= V2
(b)   V1 = (1.2) V2
(c)   V1 = (1.3) V2
(d)   V2 = (1.7) V2
(e)   V1 = (1.9) V2


QUESTION 5*

A man throws a ball with mass of 10 kg at a velocity of 2 m/s off of a stationary boat. The mass of the boat and the man together is 120 kg. What is the speed of the boat right after the ball is thrown?

(a)   0.52 m/s
(b)   0.41 m/s
(c)   0.23 m/s
(d)   0.17 m/s
(e)   0.04 m/s


QUESTION 6**

A piece of ice falls on a frozen lake and breaks up into three pieces which go off in the directions shown in the diagram below. The mass of the bigger piece is 4 kg and it moves with a speed of 4 m/s. If the two smaller pieces are 2 kg each, what would be their speed right after the breakup?

(a)   4.1 m/s
(b)   4.9 m/s
(c)   5.7 m/s
(d)   5.9 m/s
(e)   9.8 m/s


QUESTION 7*

This and the next question pertain to the following situation:

A bat strikes a ball, which has a mass of 0.1 kg and is initially moving at 40m/s toward the bat, delivering a mean force of 8400 N during a total contact time of 1 × 10-3 s. What is the magnitude of the impulse imparted to the ball by the bat? Assume that the motion is 1 dimensional.

(a)   8.4 kg m/s
(b)   8.8 kg m/s
(c)   9.5 kg m/s
(d)   11 kg m/s
(e)   19 kg m/s


QUESTION 8*

What is the speed of the ball after it is hit by the bat?

(a)   19 m/s
(b)   23 m/s
(c)   35 m/s
(d)   44 m/s
(e)   48 m/s


QUESTION 9**

Two balls are thrown against a wall. Ball A hits the wall and bounces back, while ball B sticks to the wall. Which ball acts with a greater impulse on the wall?

(a)   ball A
(b)   ball B
(c)   They are both the same.


QUESTION 10*

This and the next question pertain to the following situation:

The Earth moves around the sun in a circular orbit (approximately) once every 365.25 days (see diagram) or 3.156 × 107 seconds.

What is the Earth’s angular displacement Dq over the course of the fall semester, which is about 98 days long?

(a)   1.00 rad
(b)   1.41 rad
(c)   1.69 rad
(d)   2.23 rad
(e)   12.1 rad


QUESTION 11*

What is the Earth’s angular velocity?

(a)   1.99 × 10-7 rad/s
(b)   2.06 × 10-6 rad/s
(c)   3.11 × 10-5 rad/s
(d)   4.96 × 10-4 rad/s
(e)   1.15 × 10-3 rad/s


QUESTION 12*

This and the next two questions pertain to the following situation:

A steam locomotive has two kinds of wheels: large, driving wheels with radius 0.5 m, and small guide wheels with radius 0.25 m (see the diagram). Starting from rest, the train undergoes constant linear acceleration for 30 s. At the end of 30 s the train is moving at 10 m/s.

What is the magnitude of the angular acceleration of the driving wheels?

(a)   1/3 rad/s2
(b)   2/3 rad/s2
(c)   1 rad/s2
(d)   4/3 rad/s2
(e)   30 rad/s2


QUESTION 13*

Is the magnitude of the angular acceleration of the guide wheels greater than, less than, or equal to that of the driving wheels?

(a)   greater than
(b)   less than
(c)   equal to


QUESTION 14**

Suppose instead that the driving wheels had an angular velocity of 2 rad/s once the train had gone a distance of 48 m. Assuming, as before, that it started from rest, what would its angular acceleration have been then?

(a)   0.011 rad/s2
(b)   0.021 rad/s2
(c)   0.033 rad/s2
(d)   0.044 rad/s2
(e)   0.083 rad/s2


QUESTION 15*

This and the next question pertain to the following situation:

A man of mass 85 kg stands on one end of a uniform board of length 2 m and mass 15 kg. The other end is tied to the floor by a steel cable, and the board is supported from below just 0.5 m from the cable end (see figure).

Find the magnitude of the torque exerted by the man on the board with respect to the axis represented by the support.

(a)   850 N-m
(b)   1251 N-m
(c)   1453 N-m
(d)   1959 N-m
(e)   2057 N-m


QUESTION 16*

Suppose that the tension in the cable is T1. Now suppose the support is moved to a position 0.8 m from the cable end and that the new tension in the cable is T2. How does T1 compare to T2?

(a)   T1 > T2
(b)   T1 < T2
(c)   T1 = T2


QUESTION 17**

This and the next question pertain to the following situation:


An empty truck is loaded onto a truck scale (see figure). The weight of the truck is 10000N, of which 8000N is supported by the rear axle. If the two axles are 3m apart, how far in front of the rear axle is the truck’s center of gravity (i.e. what is the distance X)?

(a)   0.6 m
(b)   0.8 m
(c)   1.2 m
(d)   2.0 m
(e)   3.0 m


QUESTION 18***

Suppose instead that the center of mass was 0.5 m in front of the rear axle, and that the truck still weighed 10000 N. The driver has a load of weight 2000 N that he wants to put in the truck. The back of the truck is 1.5 m behind the rear axle. Is it possible for this load to tip the truck over?

(a)   yes
(b)   no


QUESTION 19*

This and the next two questions pertain to the following situation:

A skier with a mass of 50 kg starts from the top of a hill at height h. The skier glides down the hill to point A where her velocity is vA = 20 m/s and continues up a second hill 8 meters high and back down the other side. Her entire trip up to point C is frictionless. At point C she begins stopping and comes to a complete stop 48 meters later at point D.

What is the height h of the hill?

(a)   h = 11.1 m
(b)   h = 16.2 m
(c)   h = 20.4 m
(d)   h = 28.5 m
(e)   h = 33.1 m


QUESTION 20**

What is the speed vB of the skier when she reaches point B?

(a)   vB = 9.64 m/s
(b)   vB = 11.2 m/s
(c)   vB = 12.5 m/s
(d)   vB = 15.6 m/s
(e)   vB = 23.6 m/s


QUESTION 21**

What is the magnitude of the average stopping force FCD from C to D ?

(a)   FCD = 81.6 N
(b)   FCD = 208 N
(c)   FCD = 282 N
(d)   FCD = 328 N
(e)   FCD = 490 N


QUESTION 22***

The driver of an empty speeding truck slams on the brakes and skids to a stop in a distance D. If the truck were carrying a load with mass equal to its own mass, what would its stopping distance have been? (Assume the road is straight and horizontal and that the coefficient of kinetic friction is constant).

(a)   D
(b)   2D
(c)   D/2


QUESTION 23**

A force F = 4000 N is used to push a box of mass m = 5 kg mass up a q = 30° frictionless ramp that is a length L = 12 m long. Suppose the force acts parallel to the surface of the ramp, and that the box starts from rest at ground level. The force stops pushing just as the box leaves the top of the ramp, after which the box is acted on only by gravity.

What is the speed of the box VG when it hits the ground?

(a)   VG = 115 m/s
(b)   VG = 147 m/s
(c)   VG = 139 m/s
(d)   VG = 203 m/s
(e)   VG = 188 m/s


QUESTION 24**

Let the answer to the above problem be VG. If the both the length of the ramp L and the mass of the box in the above problem were doubled, what would the new speed VG,NEW of the box be as it hit the ground?

(a)   VG,NEW = 2VG
(b)   VG,NEW = 4VG
(c)   VG,NEW = VG


QUESTION 25**

A block of mass M slides down a ramp of height h0 and collides with a block of mass 2M that is initially at rest. The two blocks stick together and slide up a different ramp, reaching a maximum height h1. All surfaces are frictionless.

What is the height h1?

(a)   h0
(b)   2h0
(c)   h0/9
(d)   h0/2
(e)   h0/4