PHYS0174 Midterm Name: ___________________

Spring 2013 – 7 March 2013

Read the following instructions carefully before proceeding.

1) The exam time is 1 hour and 50 minutes. Starting time is 1:00 pm.

2) The exam is open material. You are allowed to use any testing aid you want except for

computers and phones. You cannot use the calculator on your phone.

3) Write your full name (first, last) as it appears on you student ID card in the place

indicated on every page. No additional information is required.

4) Use pens only.

5) If you have any questions, raise your hand and one of the proctors will come and answer

you.

6) When you are done, hand in the exam to one of the proctors, and exit the classroom

quietly in order not to disturb your classmates.

Name: ___________________

Problem 1

Two bodies are falling with negligible air resistance, side by side, above a horizontal plane. If

one of the bodies is given an additional horizontal acceleration during its descent, it:

A. strikes the plane at the same time as the other body

B. strikes the plane earlier than the other body

C. has the vertical component of its velocity altered

D. has the vertical component of its acceleration altered

E. follows a straight line path along the resultant acceleration vector

Ans.: __A____

Problem 2

Identical guns fire identical bullets horizontally at the same speed from the same height above

level planes, one on the Earth and one on the Moon. Which of the following three statements

is/are true?

A. The horizontal distance traveled by the bullet is greater for the Moon.

B. The change in the potential energy of the bullet when it hits the ground is the same for

both cases.

C. The flight time is less for the bullet on the Earth.

D. The velocities of the bullets at impact are the same.

Ans.: _A + C___

Problem 3

A man sits in the back of a canoe in still water. He then moves to the front of the canoe and sits

there. Afterwards the canoe:

A. is forward of its original position and moving forward

B. is forward of its original position and moving backward

C. is rearward of its original position and moving forward

D. is rearward of its original position and moving backward

E. is rearward of its original position and not moving

Ans.:___E___

Problem 4

A 640 N hunter gets a rope around a 3200 N polar bear. They are stationary, 20 m apart, on

frictionless level ice. When the hunter pulls the polar bear to him, the polar bear will move:

A. 1.0 m

B. 3.3 m

C. 10 m

D. 12 m

E. 17 m

Ans.: ___B___

Name: ___________________

Problem 5

Which one of the following five quantities CANNOT be used as a unit of potential energy?

A. wattsecond

B. gramcm/s2

C. joule

D. kgm2/s

2

E. ftlb

Ans.: __B____

Problem 6

A particle moves along the x axis under the influence of a stationary object. The net force on the

particle, which is conservative, is given by F = (8 N/m3)x

3. If the potential energy is taken to be

zero for x = 0 then the potential energy is given by:

A. (2 J/m4)x

4

B. (-2 J/m4)x

4

C. (24 J/m2)x

2

D. (-24 J/m2)x

2

E. 5 J - (2 J/m4)x

4

Ans.: ___B___

Problem 7

A boy pulls a wooden box along a rough horizontal floor at constant speed by means of a force ⃗ as shown. In the diagram f is the magnitude of the force of friction, N is the magnitude of the

normal force, and Fg is the magnitude of the force of gravity. Which of the following must be

true?

A. P = f and N = Fg

B. P = f and N > Fg

C. P > f and N < Fg

D. P > f and N = Fg

E. none of these

Ans.: ___A___

Problem 8

A forward horizontal force of 12 N is used to pull a 240 N crate at constant velocity across a

horizontal floor. The coefficient of friction is:

A. 0.5

B. 0.05

C. 2

D. 0.2

E. 20 Ans.: ___B___

Name: ___________________

Problem 9

An object placed on an equal-arm balance requires 12 kg to balance it. When placed on a spring

scale, the scale reads 12 kg. Everything (balance, scale, set of weights and object) is now

transported to the Moon where the free-fall acceleration is one-sixth that on Earth. The new

readings of the balance and spring scale (respectively) are:

A. 12 kg, 12 kg

B. 2 kg, 2 kg

C. 12 kg, 2 kg

D. 2 kg, 12 kg

E. 12 kg, 72 kg

Ans.:___C___

Problem 10

A constant force of 8.0 N is exerted for 4.0 s on a 16 kg object initially at rest. The change in

speed of this object will be:

A. 0.5 m/s

B. 2 m/s

C. 4 m/s

D. 8 m/s

E. 32 m/s

Ans.:___B___

Problem 11

At time t = 0 a 2 kg particle has a velocity of (4 m/s) ̂ - (3 m/s) ̂. At t = 3s its velocity is (2 m/s) ̂ + (3 m/s) ̂. During this time the work done on it was:

A. 4 J

B. -4 J

C. -12 J

D. -40 J

E. (4 J) ̂ + (36 J) ̂ Ans.:___C___

Problem 12

A man is marooned at rest on level frictionless ice. In desperation, he hurls his shoe to the right

at 15 m/s. If the man weighs 720 N and the shoe weighs 4.0 N, the man moves to the left with a

speed of:

A. 0

B. 2.1 10-2

m/s

C. 8.3 10-2

m/s

D. 15 m/s

E. 2.7 103 m/s

Ans.: ___C___

Name: ___________________

Problem 13

I) In the figure above, assuming that there is no friction between the mass m and the surface of

the half-sphere, at what angle will the mass m detach from the surface if it would start

sliding from rest at the top of the sphere?

A. 24.1

B. 48.19

C. 30

D. 15

Ans.: ___B___

II) What will the speed of the mass be at the point of detachment?

A. √

B.

C.

D. √

Ans.: ___D___

III) What will the velocity of the mass be at the point of detachment?

A. (

√

) ̂ (

√

√

) ̂

B. (

√

) ̂ (

√

√

) ̂

C. (

√

) ̂ (

√

√

) ̂

D. (

√

) ̂ (

√

√

) ̂

Ans.: ___D___

IV) What is the acceleration of the mass after it detaches from the sphere?

A. ( √ ) ̂ (√ ) ̂

B. ( √

) ̂ (√

) ̂

C. ̂ ̂

D. √ ̂ √ ̂

Ans.:___C___

Name: ___________________

Problem 14

A mass m1=4kg slides on a frictionless surface with an initial speed v=10m/s and collides with

another mass m2=1kg lying at rest in its path. The collision is completely inelastic and the two

masses travel together as one after the collision. After 10 seconds, the masses pass over a rough

surface with a kinetic friction coefficient k=0.5 for a total distance d=2m, and immediately after

the masses hit a spring with a spring constant k=22200N/m (see Figure).

I) What is the speed of the two masses together right after the collision and before they reach

the rough surface?

A. 12m/s

B. 8m/s

C. 10m/s

D. 6m/s

Ans.: ___B___

II) What is the speed of the masses after they go over the rough surface and before they hit

the spring?

A. 5.712m/s

B. 4.001m/s

C. 8.0m/s

D. 6.663m/s

Ans.: ___D___

III) How much will the spring compress?

A. 10cm

B. 0.22m

C. 0.01m

D. 12cm

Ans.: ___A___

IV) How much energy is lost during this process from beginning to end?

A. 98J

B. 60J

C. 89J

D. 200J

Ans.: ___C___

m1 m2

d

v=10m/s