**Excursions in Physics
**

September 15, 2000

Enter all your answers in the "scantron sheet" or the "bubble
sheet". Turn in only that sheet. Anything you write on this exam will
not be seen or used or considered or graded. Be sure your name
__and__ SSN are on the "bubble sheet" you hand in. Be sure your
name __and__ SSN are bubbled-in. Be sure your answers are recorded
correctly.

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

Possibly useful information:

v = v_{i}+ a t

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

F = m a

F_{12}= -F_{21}

w = mg

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

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

**e) none of the above**

1. Kinematics is a description of motion. Motion was first well
understood

a) by Mozart during the Orchestral Epoch.

b) by Aristotle and the ancient Greeks during the Golden Age.

c) by Ptolemy in Egypt during the Ramses Dynasty.

d) by Galileo in Italy during the Renaissance.

2. 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 astrolabe.

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

a) Euclid’s geometry.

b) Newton’s differential calculus. Newton was born the year Galileo died.

c) von Liebnitz’ integral calculus. von Liebnitz was a contemporary of Newton's.

d) Rubick’s cubism. Rubick lived in the twentieth century (and is probably still alive).

4. Velocity is the time rate of change of

a) acceleration.

b) speed.

c) displacement.

d) momentum.

5. Acceleration is the time rate of change of

a) velocity.

b) displacement.

c) distance.

d) momentum.

6. 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.

7. What is the average speed of a car that travels 250 km in 5 h?

a) 1250 km/h

b) 625 km/h

c) 50 km/h;= 250^{km}/_{5 h}= 50^{km}/_{h}

d) 25 km/h

8. Consider a train that has an acceleration of 3 m/s^{2}.
Initially, at time t = 0, it has a velocity of v_{i }= 30
m/s. What is its speed at t = 4 s?

a) 64 m/s

b) 44 m/s

c) 29 m/s

d) 12 m/s

e) none of the above; v = v_{i}+ a t = ( 30^{m}/_{s}) + ( 3 m/s^{2})( 4 s ) = (30 + 12) m/s = 42 m/s

9. Consider a car that starts at **rest
****( v _{i} = 0 )** and
accelerates at 3 m/s

a) 18 m/s

b) 12 m/s; v = v_{i}+ a t = ( 0 ) + ( 3 m/s^{2})( 4 s ) = 12 m/sc) 9 m/s

d) 6 m/s

10. Consider a car that starts at **rest** **
****( v _{i} = 0 )** a and
accelerates at 3 m/s

At that time, t = 4 s, how ** far** has it
gone?

a) 48 m

b) 24 m;x = x_{i }+ v_{i}t + (^{1}/_{2}) a t^{2}

x = 0 + 0 + (^{1}/_{2}) ( 3 m/s^{2})( 4 s )^{2}

x = (^{1}/_{2}) ( 3 m/s^{2})( 16 s^{2})

x = 24 mc) 12 m

d) 6 m

11. Consider a ball that is thrown upward at the edge of a canyon
with an initial velocity of 20 m/s. Three seconds later, what is
its ** velocity**?

a) 30 m/s

b) 15 m/s

c) - 10 m/s;v = v_{i}+ a t = ( 20 m/s ) + ( - 10 m/s^{2})( 3 s ) = (20 - 30) m/s = - 10 m/sd) - 30 m/s

12. Consider a ball that is thrown straight upward at the edge of a
canyon with an initial velocity of 20 m/s. Three seconds later,
** where** is it located? Take its initial position, at the
edge of the canyon, to be the origin; that is, y

a) 30 m

b) 15 m;x = x_{i }+ v_{i}t + (^{1}/_{2}) a t^{2}

y = y_{i }+ v_{yi}t + (^{1}/_{2}) a_{y}t^{2}

y = y_{i }+ v_{yi}t + (^{1}/_{2}) ( - g ) t^{2}

y = 0+ ( 20 m/s ) ( 3 s) + (^{1}/_{2}) ( - 10 m/s^{2}) ( 3 s )^{2}

y = 0+ 60 m - (^{1}/_{2}) ( 10 m/s^{2}) ( 9 s^{2})

y = 0+ 60 m - 45 m

y = 15 mc) - 10 m

d) - 30 m

13. A rock climber dislodges a rock and notices that it falls for
5 seconds before hitting the canyon floor below. How
** fast** is it going when it strikes the canyon floor?

a) 10 m/s

b) 15 m/s

c) 25 m/s

d) 50 m/s;v = v_{i}+ a t

v = 0 + ( - 10 m/s^{2}) ( 5 s )

v = - 50 m/s (for the velocity with the minus sign meaning "down")

v = 50 m/s (for the "speed" or simply "how fast")

- d) 250 m

14. A rock climber dislodges a rock and notices that it falls for 5
seconds before hitting the canyon floor below. How ** far**
has it fallen when it strikes the canyon floor?

a) 10 m

b) 60 m

c) 125 mx = x_{i }+ v_{i}t + (^{1}/_{2}) a t^{2}

y = y_{i }+ v_{yi}t + (^{1}/_{2}) a_{y}t^{2}

y = y_{i }+ v_{yi}t + (^{1}/_{2}) ( - g ) t^{2}

y = 0+ 0 + (^{1}/_{2}) ( - 10 m/s^{2}) ( 5 s )^{2}

y = 0+ 0 + (^{1}/_{2}) ( - 10 m/s^{2}) ( 25 s^{2})

y = 125 md) 250 m

15. 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 is 5 m above the driveway below. How far from the
building does the ball strike the driveway?

a) 5 m

b) 10 m

c) 15 m

d) 20 mFirst, we must ask "how long is it in the air?"y = (^{1}/_{2}) a_{y}t^{2}

y = (^{1}/_{2}) ( - g ) t^{2}

When it hits the driveway, its vertical position is y = - 5 m, 5 m below where it started.- 5 m = (^{1}/_{2}) ( - 10 m/s^{2}) t^{2}

1 s^{2}= t^{2}

1 s = t

Now, how farhorizontallydoes it travel in this time?x = v t

x = ( 20 m/s ) ( 1 s )

x = 20 m

16. 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

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

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

17. 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) 1.0 s

b) 2.0 s

c) 4.0 sFirst, we must ask "how long is it in the air?"y = y + v+_{yi}(^{1}/_{2}) a_{y}t^{2}is somewhat difficult to solve. Aneasierapproach is to use

v_{y}= v_{yi}+ a_{y}t

When it gets back to the level surface, v_{y}= - v_{yi}- 20 m/s = 20 m/s + ( - 10 m/s^{2}) t

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

4 s = td) 8.0 s

y = (^{1}/_{2}) ( - g ) t^{2}

- 5 m = (^{1}/_{2}) ( - 10 m/s^{2}) t^{2}

1 s^{2}= t^{2}

1 s = t

Now, how farhorizontallydoes it travel in this time?x = v t

x = ( 20 m/s ) ( 1 s )

x = 20 m

18. 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) 15 m

c) 20 mFrom the previous problem, we know it is in the air for t = 4.0 s

How farhorizontallydoes it travel in this time?x = v t

x = ( 5 m/s ) ( 4 s )

x = 20 md) 40 m

19. Consider two children on a playground merry-go-round. One is near
the center and one is near the edge. The child near the edge

a) requires more time to make one revolution than

b) travels slower than

c) requires less time to make one revolution than

d) makes one revolution in the same time as the child near the center.

20. If a Ferris wheel has a radius of 10 m and requires 20 seconds to make a revolution, what is the linear speed of a passenger? C = 2 ÷ r; ÷ = 3.14

a) 0.78 m/s

b) 1.57 m/s

c) 3.14 m/s

v = ( 2 ÷ r ) / (20 s)

v = [ 2 (3.14) (10 m) ] / ( 20 s )

v = 62.8 m / 20 s

v = 3.14 m/sd) 9.80 m/s

21. 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

c) continue in motion with the same speed along the same straight line

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

22. 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."

c) "The acceleration of an object is proportional to the net force on the object and inversley proportional to the object's mass."

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

23. 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.

c) The net force on an object is equal to the product of the mass of that object and its acceleration.

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

24. Mass is a measure of

a) the volume of an object.

b) the size of an object.

c) how difficult it is to change the motion of an object.

d) the acceleration of an object.

25. The weight of an object is

a) another name forthe mass of an object.

b) the sum of all the forces on an object.

c) the force of gravity on an object.

d) always greater than the mass, even in a vacuum.

26. The net force on a 10-kg object, ** at rest**, is

a) 98 N

b) 49 N

c) 10 N

d) zero; The net force onanyobject at rest must be zero!

27. The net force on a 10-kg object, i** n free fall**,
is

a) 98 NF = ma

F = (10 kg) (9.8 m/s^{2})

F = 98 Nb) 49 N

c) 10 N

d) zero

28. 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 NThe rope only pulls up on Harry once and the forceupmust equal the forcedown.c) 250 N

d) 25 N

29. A force of 24 N acts on an object whose mass is 6 kg. This causes
the object to accelerate at

a) 2 m/s^{2}

b) 3 m/s^{2}

c) 4 m/s^{2}F = m a

24 N = ( 6 kg ) a

a = 4 m/s^{2}d) 6 m/s

^{2}

30. A car, with mass of 1,000 kg, accelerates at 3
m/s^{2}. The net force exerted on the car must be

a) 333 N

b) 1,000 N

c) 1,500 N

d) 3,000 NF = m a

F = ( 1,000 kg ) ( 3 m/s^{2})

F = 3,000 N

31. The weight of a 1,000-kg car is

a) 500 N

b) 1,000 N

c) 2,000 N

d) 10,000 Nw = m g

w = ( 1,000 kg ) ( 10 m/s^{2})

w = 3,000 N

32. What is the ** mass** of a fireman whose

a) 9.8 kg

b) 25 kg

c) 50 kgw = m g

500 N = m ( 10 m/s^{2})

50 kg = md) 500 kg

33. A fireman, whose ** weight** is 500 N

a) 50 N

b) 150 N

c) 450 NWhen we write Newton's Second Law,F = m a

the "F" in that equation isalwaysthenetforceF_{net}= m a = ( 50 kg) ( 1 m/s^{2})

F_{net}= 50 N

What forces make up thisnetforce?F_{net}= F_{gravity}- F_{friction}F_{gravity}= w = 500 N

50 N = 500 N - F_{friction}

F_{friction}= 450 Nd) 550 N

34. Suppose you are driving along in an open car and throw a ball
straight up into the air. While the ball is still in the air you step
down on the **accelerator**. Where does the ball land relative to
the car?

a) behind the car

b) back into the car

c) in front of the car

35. 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 mast.

b) at the base of the mast.

c) behind the base of the mast.

36. 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.

c) made great advances in Mechanics, Gravity, Optics, and Mathematics.

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

37. Galileo

a) may be called the Father of Modern Optics.

b) wrote his findings in common Italian while at the University of Paducah.

c) may be called the Father of Modern Science.

d) wrote his findings about Gravity and discovered calculus.

38. 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.

b) predictions of theories must be tested by and agree with experimental results.

c) theories must have elegant mathematical equations.

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

39. When an object moves in a circle, Newton's Second Law of Motion, F = ma, says that object must have a net force on it

a) only if its speed is changing.

b) directed toward its forward motion.

c) in the upward direction.

d) directed toward the center of the circle.

40. What value will the spring scale read in the system shown
here?

a) zero

b) 50 N

c) 100 N

d) 200 N

41. In the sketch here, what value will the scale read if the little girl's weight is 250 newtons.

a) zero

b) 125 NThat isone-halfher weight. The cord pulls up with that force on her left handandon her right hand. Thesumof the forces up equals the force of gravity pulling down.c) 250 N

d) 500 N

42. The four fundamental forces are

a) gravity, friction, electricity, and atomic

b) gravity, electromagnetic, strong nuclear, and weak nuclear

c) gravity, strong electric, weak electric, and atomic

d) gravity, friction, air resistance, and atomic

43. “Projectile motion” describes the two-dimensional motion of an object under the influence of gravity. The path that such an object takes is known as

a) an ellipse.

b) a hyperbola.

c) a parabola.

d) a semi-circle.

44. A moving object on which no forces are acting will continue to
move with constant

a) acceleration.

b) velocity.

c) centriptel acceleration.

d) displacement.

45. Sir Isaac Newton and Baron Gottfried Wilhelm von Liebnetz had a controversy over which of them had discovered or invented

a) Rubick’s Cube.

b) Euclid’s Geometry.

c) calculus.

d) algebra.

46. Weight is the force of gravity on an object. The weight of a
one-kilogram mass is

a) 2.2 newtons.

b) 5.6 newtons.

c) 9.8 newtons.

d) 19.6 newtons.

47. A stone is dropped (from rest) from a bridge, high above a
river. The stone takes **five seconds** before it hits the river.
How fast is it going when it hits the water?

a) 5 m/s

b) 10 m/s

c) 50 m/sv_{y}= g t

v_{y}= ( 10 m/s^{2}) ( 5 s )

v_{y}= 50 m/sd) 100 m/s

48. A stone is dropped (from rest) from a bridge, high above a
river. The stone takes **five seconds** before it hits the river.
How high is the bridge above the water?

a) 10 m

b) 25 m

c) 125 my = (^{1}/_{2}) g t^{2}

y = (^{1}/_{2}) ( 10 m/s^{2}) ( 5 s )^{2}

y = (^{1}/_{2}) ( 10 m/s^{2}) ( 25 s^{2})

y = 125 md) 250 m

49. 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 sAs with question 17, first we must ask "how long is it in the air?"y = y + v+_{yi}(^{1}/_{2}) a_{y}t^{2}is somewhat difficult to solve. Aneasierapproach is to use

v_{y}= v_{yi}+ a_{y}t

When it gets back to the level surface, v_{y}= - v_{yi}- 15 m/s = 15 m/s + ( - 10 m/s^{2}) t

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

3 s = td) 4.0 s

50. 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 mFrom the previous question, we know the ball is in the air for t = 3.0 s

How far, horizontally, does it travel in that time?

The horizontal motion is atcontstantvelocityx = v t

x = ( 8 m/s ) ( 3 s )

x = 24 m/sd) 48 m

(C) 2003; Doug Davis; all rights reserved