**Excursions in Physics
**

First Hour Exam

February 1, 2002

Statistics:

High: 100 (2!)

Mean: 82

Low: 52

For every question, also consider the following as a possible answer:

**e) none of the above**

Possibly useful information:

v = ^{x }/
_{t}

a = ^{v}
/ _{t}

v = v_{i} + a t

x = x_{i}+ v_{i} t + (^{1}/_{2}) a t^{2}

v = r

F = m a

**F**_{12} = – **F**_{21}

w = m g

g = 9.8 m/s^{2}
10 m/s^{2}

For every question, also consider the following as a possible answer:

1. Kinematics is a description of motion. Motion was first well understood
by Galileo in Italy at the time of the Renaissance. Dynamics is an explanation
of the cause and effect of motion. Dynamics can be understood by the Laws of
Motion developed by

a) Aristotle

b) Ptolemy

**c) Newton**

d) Joule

2. To measure the time needed to investigate motion,

a) Aristotle used a sundial.

b) Ptolemy used the pendulum clock which had just been invented.

**c) Galileo invented his own water clocks.**

d) Newton invented the pendulum clock.

3. Galileo took a position as a professor of mathematics and taught

a) Rubick’s cubism

b) Newton’s differential calculus

c) von Liebnetz’ integral calculus

**d) Euclid’s geometry**

4. Galileo was given a lifetime pension by the “city fathers” of Venice
because he introduced

a) the pendulum clock.

b) the water clock.

**c) the telescope.**

d) the sun dial.

5. To calculate the average speed of an object, we need to know

a) force and mass.

**b) distance and time.**

c) distance and mass.

d) force and time.

6. Velocity is the time rate of change of

a) acceleration.

b) speed.

**c) displacement.**

d) momentum.

7. Acceleration is the time rate of change of

**a) velocity.**

b) displacement.

c) distance.

d) momentum.

8. Acceleration might be described as telling

a) where an object is located relative to an origin or reference point.

b) how fast something is moving.

**c) how fast something is getting faster.**

d) how long an object has been moving.

9. What is the average speed of a motorcycle that travels 150 m in 30 s?

**a) 5 m/s**; v = 150 m/30 s = 5 m/s

b) 10 m/s

c) 50 m/s

d) 450 m/s

10. What is the average speed of a car that travels 125 km in 5 h?

a) 625 km/h

**b) 25 km/h**; v = 125
km/5 h = 25 km/h

c) 10 km/h

d) 9.8 km/h

11. Consider a car that starts__ at__ __rest__ (v_{i}
= 0) and accelerates at 2 m/s^{2} for 4 seconds.

At that time, t = 4 s, how ** fast** is it going?

a) 16 m/s

b) 12 m/s

d) 4 m/s

12. Consider a car that starts

At that time, t = 4 s, how

a) 32 m

b) 24 m

d) 8 m

13. Consider a train that has an acceleration of 3 m/s^{2}. Initially,
at time t = 0, it has a velocity of v_{i }= 20 m/s. What
is its speed at t = 3 s?

a) 57 m/s

b) 41 m/s

**c) 29 m/s**; v = v_{i}
+ a t = 20 m/s + (3 m/s^{2})(3 s) = 20 m/s + 9 m/s = 29 m/s

d) 9 m/s

14. Consider a ball that is thrown upward at the edge of a canyon with an initial
velocity of 30 m/s. Four seconds later, what is its ** velocity**?

a) 40 m/s

b) 20 m/s

d) - 30 m/s

15. Consider a ball that is thrown straight upward at the edge of a canyon with an initial velocity of 30 m/s. Four seconds later,

y = 0 + 120 m - 80 m = 40 m

b) 20 m

c) 110 m

d) 130 m

16. Consider a ball thrown ** horizontally** from the edge of a building
with an initial velocity of 20 m/s. The ball is thrown from 5 m above the
ground. How

a) 0.5 s

y = - 5 m =

1 s

1 s = t

c) 1.5 s

d) 2.0 s

17. Consider a ball that is thrown ** horizontally** from the edge
of a building with an initial velocity of 20 m/s. The ball is thrown from 5
m above the ground.

a) 5 m

b) 10 m

c) 15 m

18. When a ball or stone or other object is thrown or hit or fired, and air resistance can be neglected, the resulting motion is known as projectile motion. The path of an object in projectile motion is

a) a quadrant of a circle

b) a hyperbola

d) a straight line

19. Projectile motion is a combination of

a) horizontal motion with constant, non-zero acceleration and vertical motion with constant velocity

b) horizontal motion with constant non-zero acceleration and vertical motion with constant, non-zero acceleration

d) horizontal motion with constant velocity and vertical motion with constant velocity

20. Consider a ball thrown from a level surface with an initial upward velocity
of 20 m/s and an initial horizontal velocity of 5 m/s. __How__** long**
is the ball in the air?

a) 0.5 s

b) 1.0 s

c) 2.0 s

- 40 m/s = ( - 10 m/s

4 s = t

t = 4 s

[[ The **key** was correct ]]

21. Consider a ball thrown from a level surface with an initial upward velocity
of 20 m/s and an initial horizontal velocity of 5 m/s. ** Where** does
it land? That is, measured from its initial position, where does it come back
to and strike the level surface?

a) 5 m

b) 10 m

c) 15 m

[[ The **key** was correct ]]

22. A golf ball is given a velocity of 8 m/s horizontally and 15 m/s vertically.
__How long__ is it in the air, before coming back to its initial vertical
height? That is, __how long__ is it in the air before striking the level
ground?

a) 1.5 s

b) 2.0 s

**c) 3.0 s**; v = v_{i}
+ a t

v = - 15 m/s = 15 m/s + ( - 10 m/s^{2}) t

- 30 m/s = ( - 10 m/s^{2}) t

t = 3 s

d) 4.0 s

23. A golf ball is given a velocity of 8 m/s horizontally and 15 m/s vertically.
__How far__, horizontally, does it travel before coming back to its initial
vertical height? That is, __how far__ does it travel before hitting the level
ground?

a) 8 m

b) 12 m

**c) 24 m**; x = v_{x}
t = (8 m/s) (3 s) = 24 m

d) 48 m

**
**24. If a Ferris wheel has a diameter of 10 m (that
means r = 5 m) and requires 20 seconds to make a revolution, what is
the linear speed of a passenger? C = 2
r; = 3.14

a) 0.8 m/s

c) 3.1 m/s

d) 6.3 m/s

25. Newton's First Law of Motion states that, in the absence of a net force, an object in motion will

a) eventually come to rest

b) continue in motion but slow down until it stops

d) continue along the same straight line with a decrease in speed

26. Newton's Second Law of Motion explains the cause of motion and may be stated as

a) "All motion is relative."

b) "All objects fall with the same velocity."

d) "The acceleration of an object is proportional to the product of the object's mass and the net force on it."

27. Newton's Second Law of Motion explains the cause of motion and may be stated as

a) The net force on an object is inversely proportional to its weight.

b) The net force on an object produces an acceleration that is proportional to the time of action of that force.

d) The net force on an object is inversely proportional to the mass of the object.

28. Newton’s Third Law of Motion explains how two objects interact and may be stated as

a) "All motion is relative."

b) "All objects fall with the same velocity."

d) "The acceleration of an object is proportional to the product of the object's mass and the net force on it."

29. Mass is a measure of

a) the volume of an object

b) the size of an object

d) the velocity of an object

30. The weight of an object is

a) the same thing as the mass of an object

b) the sum of all the forces on an object

d) always less than the mass, even in a vacuum

31. The net force on a 1-kg object,

a) 9.8 N

b) 4.9 N

c) 1.00 N

32. The net force on a 1-kg object,

b) 4.9 N

c) 1.00 N

d) zero

33. Harry the Painter has a weight of 500 N. When he is suspended as shown in the sketch here, what is the tension in the rope?

a) 1000 N

b) 500 N

**c) 250 N**; The rope pulls UP on Harry TWICE.

d) 25 N

34. What will the spring scale read in the arrangement shown here?

a) zero

b) 50 N

**c) 100 N**

d) 200 N

35. A force of 24 N acts on an object whose mass is 8 kg.

This causes the object to accelerate at

a) 2 m/s^{2}

**b) 3 m/s ^{2}**

c) 6 m/s

d) 12 m/s2

36. What is the **mass** of a fireman whose ** weight** is 500
N?

a) 5000 kg

b) 500 kg

d) 5 kg

37. A fireman, whose

a) 90 N

b) 150 N

F

F

d) 500 N

38. If a sailor drops a wrench from the top of a tall mast on a moving ship, it will fall and hit the deck

a) in front of the base of the.

c) behind the base of the mast.

39. Sir Isaac Newton

a) first discovered the Law of Falling Bodies while at the University of Pisa.

b) was a close friend of Liebnitz and encouraged his early development of calculus.

d) used water clocks of his own invention to aid sailors in determining their longitude.

40. The hallmark of Modern Science is that

a) theories are accepted or rejected based upon the background or reputation of the scientists who propose them (horrors!)

c) theories must have elegant mathematical equations.

d) predictions of theories must not contradict established authorities (such as Plato or Pythagores)

41. When applying Newton's Second Law of Motion, F = ma,

a) F is always the largest force present.

c) m is always the largest mass in the system.

d) m must be the smallest mass in the system.

42. Consider a 2-kg laboratory cart which accelerates at 3 m/s

a) 2 N

b) 3 N

d) 12 N

43. Consider a 2-kg lab cart which has an initial velocity of 5 m/s and then
accelerates at 3 m/s^{2} for four seconds. At that time, t = 4 s, how
**fast** is it moving?

a) 20 m/s

**b) 17 m/s;** v = v_{i}
+ a t = 5 m/s + (3 m/s^{2})(4 s) = (5 + 12) m/s = 17 m/s

c) 12 m/s

d) 8 m/s

44. Consider a 2-kg lab cart which has an initial velocity of 5 m/s and then
accelerates at 3 m/s^{2} for four seconds. At that time, t = 4 s, how
**far** has it moved?

a) 48 m

**b) 44 m**; x = x_{i}
+ v_{i} t + (1/2) a t^{2} = 0 + (5 m/s)(4 s) + (1/2)(3 m/s^{2})(4
s)^{2}

x = (0 + 20 + 24) m = 44 m

c) 32 m

d) 24 m

45. In the absence of air resistance,

a) heavier objects fall with a greater acceleration than lighter objects.

**b) heavier objects fall with the same acceleration
as lighter objects.**

c) heavier objects fall with a smaller acceleration than lighter objects.

46. A roller coaster is launched from rest to 28 m/s (that’s about 100
km/h or 60 mi/h) in 3.5 seconds. That is an acceleration of

a) 2 m/s^{2}

b) 4 m/s^{2}

**c) 8 m/s ^{2};**
a = v/t
= (28 m/s)/(3.5 s) = 8 m/s

d) 12 m/s

The Rock 'n' Roller Coaster at the Disney-MGM Studios
inWalt Disney World launches from rest to 60 mi/h in 2.8 seconds for an acceleration
of about 9.6 m/s^{2}.

47. A particular roller coaster is launched with an acceleration of 5 m/s^{2}.
What is the net force required to launch a 1,000-kg car?

a) 200 N

b) 1,000 N

**c) 5,000 N**; F = m
a = (1 000 kg)(5 m/s^{2}) = 5 000 N

d) 10,000 N

48. When any object moves in a circle

a) its speed must decrease

**b) its acceleration continues to change direction**;
its acceleration always points toward the center

c) its velocity is directed toward the center of the circle

d) its acceleration is tangent to the circle

49. The net force on any object which moves in a circle

a) causes the speed to increase.

b) is directed along a line tangent to the circle.

c) increases as the object slows down.

**d) points toward the center of the circle.**

50. When using Newton's Third Law of Motion, **F**_{12} = - **F**_{21},
the two forces

a) always cancel so this applies only to systems in equilibrium.

**b) always act on different objects.**

c) must act on the same object.

d) are always perpendicular to each other.