Fall 2007 Physics 101 Hour Exam 1(24 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 ***.

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 114. The exam period was 90 minutes; the mean score was 88.1; the median score was 91. Click here to see page1 page2 of the formula sheet that came with the exam.

QUESTION 1*

This and the following three questions concern the same physical situation.

A car moves with velocity v0= 12 m/s on a slick road when the driver applies the brakes. The wheels slide and it takes the car 4 seconds to stop with a constant deceleration.

Which of these pairs of graphs correctly shows the displacement and the velocity of the car during the time when it decelerates?

(a)
(b)
(c)

QUESTION 2*

How far does the car go before it stops?

(a)   12 m
(b)   24 m
(c)   48 m

QUESTION 3**

When the velocity of the car has decreased to half its initial velocity the remaining distance is

(a)   greater than half the total distance required to stop.
(b)   half the total distance required to stop.
(c)   less than half the total distance required to stop.

QUESTION 4*

What is the kinetic friction coefficient μk between the car and the road surface?

(a)   0.13
(b)   0.31
(c)   0.62
(d)   1.50
(e)   6.00

QUESTION 5*

This and the following two questions concern the same physical situation.

Three strings hold a block of mass M in place, as shown in the figure above. The string on the upper right pulls with a force of 141.0 N. The string on the lower right pulls with a force of 14.1 N. Gravity points in the -y direction.

What is the magnitude of the tensionTL in the string on the left?

(a)   90 N
(b)   100 N
(c)   110 N
(d)   127 N
(e)   155 N

QUESTION 6*

What is the mass M?

(a)   5.2 kg
(b)   7.0 kg
(c)   9.2 kg
(d)   12.7 kg
(e)   15.5 kg

QUESTION 7*

What is the vertical component of the tension in lower right string, the T1y, pulling at the mass M?

(a)   -10.0 N
(b)   0.0 N
(c)   10.0 N

QUESTION 8**

This and the following question concern the same physical situation.

A block of mass 15 kg hangs on a massless string connected via a pulley to a block of mass 40 kg, which rests on a 30° incline, as shown.

There is static friction between the incline and the 40 kg block. The two blocks remain at rest. The static friction coefficient μs must be at least

(a)   0.051
(b)   0.145
(c)   0.312
(d)   0.409
(e)   0.552

QUESTION 9*

We pour oil on the incline, so the incline becomes frictionless. Which of the following statements becomes true?

(a)   The 40 kg block will slide down the incline, pulling the 15 kg block up.
(b)   The blocks will stay at rest.
(c)   The 15 kg block will fall down, pulling the 40 kg block up the incline.

QUESTION 10*

Mr. Smith flies on an airplane, traveling 3000 miles at 500 miles/hour. He then rides a train for 2 hours at 100 miles/hour, and finally rides a bus for 100 miles at 60 miles/hour. His average speed is, approximately,

(a)   110 m/h
(b)   280 m/h
(c)   340 m/h
(d)   390 m/h
(e)   410 m/h

QUESTION 11*

A Mars Rover pulls a rock across a horizontal surface on Mars, bringing it from rest to a final velocity of 1 mile per hour. The kinetic friction coefficient between the rock and the Mars surface is μk = 0.05. Which one of the following two forces are NOT equal to each other while the Mars Rover speeds up?

(a)   The force of the Mars Rover pulling on the rock and the frictional force between the rock and the Martian surface.
(b)   The normal force on the rock by the Martian surface and the gravitational force of Mars on the rock.
(c)   The gravitational force of Mars on the rock and the gravitational force of the rock on Mars.

QUESTION 12**

Sally is riding on an elevator. Suddenly she feels lighter. Which of the following is true?

(a)   The elevator is speeding up.
(b)   The elevator is slowing down.
(c)   There is not enough information to tell.

QUESTION 13*

Fred is riding on a rocket accelerating upward from the surface of the Earth with acceleration a = 29.4 m/s2. Fred's mass is 80 kg. What is his apparent weight?

(a)   2145 N
(b)   3136 N
(c)   4166 N

QUESTION 14**

A box with mass m = 10 kg is pushed at constant speed across the floor of an elevator by a force F = 120 N, parallel to the floor of the elevator. The coefficient of friction of the floor is μK = 0.6. What is the acceleration of the elevator?

(a)   10.2 m/s2
(b)   15.6 m/s2
(c)   18.4 m/s2
(d)   19.3 m/s2
(e)   22.8 m/s2

QUESTION 15*

This and the following three questions concern the same physical situation.

A cannon fires a cannon ball at an angle of 25°, measured from the ground as shown. At the moment the cannon ball is fired, the y component of its velocity, vy0, is 8.45 m/s. The cannon ball lands 31.25 m away.

What is vx0, the x-component of the cannon ball's initial velocity?

(a)   8.5 m/s
(b)   10.2 m/s
(c)   13.4 m/s
(d)   16.1 m/s
(e)   18.1 m/s

QUESTION 16*

What is the maximum height, h, that the ball will reach?

(a)   0.44 m
(b)   1.57 m
(c)   2.98 m
(d)   3.64 m
(e)   4.02 m

QUESTION 17*

Right before it hits the ground the y component of the ball's velocity vy is:

(a)   8.45 m/s
(b)   -8.45 m/s
(c)   10.05 m/s
(d)   -10.05 m/s
(e)   20 m/s

QUESTION 18*

If vy0 were halved (i.e. made two times smaller) how high would the cannon ball go?

(a)   h/4
(b)   h/2
(c)   h

QUESTION 19*

This and the following question concern the same physical situation.

You are riding on a northward-bound train, which is moving at a speed of 30 mi/hr. You walk South with speed 3 mi/hr with respect to the train. Your speed with respect to the ground would be

(a)   3 mi/hr
(b)   27 mi/hr
(c)   30 mi/hr
(d)   33 mi/hr
(e)   Can't tell from the information given.

QUESTION 20**

If you instead walked northeast at 3 mi/hr with respect to the train, what would be your relative speed with respect to the ground?

(a)   29.52 m/s
(b)   30.98 m/s
(c)   31.06 m/s
(d)   32.19 m/s
(e)   33.05 m/s

QUESTION 21**

This and the following question concern the same physical situation.

Olivia is riding on a roller coaster, which moves at constant speed throughout the ride. Unfortunately, the attendant forgot to lock her in before the roller coaster departed, and now she is headed for a loop of radius 20 m.

What is the minimum speed of the roller coaster on top of the loop such that Olivia does not fall out at the top of the loop?

(a)   2 m/s
(b)   6 m/s
(c)   10 m/s
(d)   14 m/s
(e)   21 m/s

QUESTION 22**

Olivia has a mass of 65 kg. If the roller coaster is traveling 22 m/s, what is the normal force acting on her at the top of the loop?

(a)   407 N
(b)   612 N
(c)   827 N
(d)   936 N
(e)   1042 N

QUESTION 23***

This and the following question concern the same physical situation.

Harvey is riding a carnival ride which consists of a cylindrically shaped room of radius R = 8 m rotating on its axis with angular velocity ω. Harvey's mass is 85 kg. The floor drops out from below Harvey's feet, and he sticks to the wall rather than descending with the floor. The coefficient of static friction of the wall, μs = 7.66 .

The angular velocity must be at least

QUESTION 24**

If Harvey's mass doubled, what would this mean for the answer to the previous question?

(a)   ω would have to be twice as large.
(b)   ω; could be half as large.
(c)   ω would not need to change.

Scoring of True-False (T,F) Questions:
• If you mark the correct answer, you get 2 points.
• If you mark the wrong answer or if you mark neither answer, you get 0 points.
Scoring of Multiple Choice I (a,b,c) Questions:
• If you mark the correct answer, you get 3 points.
• If you mark a wrong answer or if you mark none of the answers, you get 0 points.
Scoring of Multiple Choice II (a,b,c,d,e) Questions:
• If you mark one answer and it is the correct answer, you get 6 points.
• If you mark two answers and one of them is the correct answer, you get 3 points.
• If you mark three answers and one of them is the correct answer, you get 2 points.
• If you do not mark the correct answer, or if you mark more than three answers, or if you mark none of the answers, you get 0 points.