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Physics - Kinematics Flashcards

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1
Q

the rate of change of velocity with time. It is measured in metres per second^2.

A

acceleration

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2
Q

the forces that are in opposition to the relative motion of an object as it passes through the air.

A

air resistance

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3
Q

The vector sum of forces acting on an object that is not accellerating equals zero (ΣF=0)

A

the equilibrium rule

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4
Q

In science, ___ is the push or pull on an object with mass that causes it to change velocity (to accelerate). ___ represents as a vector, which means it has both magnitude and direction.

A

Force

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5
Q

In Newtonian physics, ___ is any motion of a body where gravity is the only force acting upon it. No air resistance.

A

free fall

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6
Q

The force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.

A

Friction

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7
Q

the resistance of any physical object to any change in its velocity. This includes changes to the object’s speed, or direction of motion. An aspect of this property is the tendency of objects to keep moving in a straight line at a constant speed, when no forces act upon them.

A

Inertia

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8
Q

the base unit of mass in the metric system, formally the International System of Units (SI), having the unit symbol kg

A

kilogram

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9
Q

___ is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied. An object’s ___ also determines the strength of its gravitational attraction to other bodies.

A

Mass

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10
Q

___ the vector sum of forces acting on a particle or body. The ___ is a single force that replaces the effect of the original forces on the particle’s motion. It gives the particle the same acceleration as all those actual forces together as described by the Newton’s second law of motion.

A

Net force

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11
Q

the International System of Units (SI) derived unit of force.

A

Newton (unit)

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12
Q

the ___ of an object is the magnitude of the change of its position; it is thus a scalar quantity. The average ___ of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; the instantaneous ___ is the limit of the average ___ as the duration of the time interval approaches zero.

A

Speed

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13
Q

A force that completely balances the weight of an object at rest.

A

support force

(normal force)

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14
Q

in physics, a quantity that is typically represented by an arrow whose direction is the same as that of the quantity and whose length is proportional to the quantity’s magnitude.

A

Vector

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15
Q

in physics, a quantity that has both magnitude and direction. It is typically represented by an arrow whose direction is the same as that of the quantity and whose length is proportional to the quantity’s magnitude.

A

Vector

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16
Q

___ is defined as a vector measurement of the rate and direction of motion. Put simply, ___ is the speed at which something moves in one direction. The speed of a car traveling north on a major freeway and the speed a rocket launching into space can both be measured using ___.

A

Velocity

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17
Q

the space that a substance (solid, liquid, gas, or plasma) or shape occupies or contains. ___ is often quantified numerically using the SI derived unit, the cubic metre.

A

Volume

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18
Q

The ___ of an object is the force of gravity on the object and may be defined as the mass times the acceleration of gravity, w = mg. Since the ___ is a force, its SI unit is the newton. Density is mass/volume.

A

weight

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19
Q

Kinematics is the study of:

motion
physical therapy
time
forces

A

motion

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20
Q

An ant zig-zags back and forth on a picnic table as shown. The ant’s distance traveled and displacement are

55 cm and 55 cm.
25 cm and 55 cm.
55 cm and 25 cm.
55 cm and –55 cm.
55 cm and –25 cm.

A

55 cm and –25 cm.

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21
Q

What term describes how fast an object is moving and in what direction?

Speed
Velocity
Acceleration
Free fall

A

Velocity

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22
Q

What term describes how fast an object is moving without considering its direction?

Speed
Velocity
Acceleration
Free fall

A

Speed

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23
Q

The drawing shows the position of a rolling ball at one second intervals. Which one of the following phrases best describes the motion of this ball?

constant position
constant velocity
increasing velocity
constant positive acceleration
decreasing velocity

A

constant velocity

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24
Q

Δ is defined as:

final minus the initial value
change in the final value
initial minus the final value
change in the initial value

A

final minus the initial value

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25
Q

Which one of the following equations describes the distance traveled at a constant velocity?

d = v/t
d = vt
d = 1/2vt
none of these

A

d = vt

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26
Q

Which term describes the rate at which velocity is changing with time?

Speed
Velocity
Acceleration
Free fall

A

Acceleration

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27
Q

An object is moving to the right (+ direction), but its acceleration is negative. The object is:

stopped
speeding up
moving at a constant velocity
slowing down

A

slowing down

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28
Q

Which one of the following is not a vector quantity?

velocity
speed
displacement
acceleration

A

speed

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29
Q

If an object is accelerating from rest at 20 m/s/s, approximately how fast is it going after 5 s?

4 m/s
10 m/s
50 m/s
100 m/s

A

100 m/s

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30
Q

Which term describes an object falling under the influence of gravity with no air-resistance?

Speed
Velocity
Acceleration
Free fall

A

Free fall

31
Q

For an object dropped from rest, which of the following is true?

acceleration increases with time
velocity remains constant
velocity increases linearly
distance traveled increases linearly

A

velocity increases linearly

32
Q

A base ball is hit straight up into the air at a speed of 20 m/s. How long does it take to reach the high-point in its trajectory.

1/2 seconds
1 second
2 seconds
4 seconds
5 seconds
10 seconds
20 seconds

A

2 seconds

33
Q

A baseball is hit vertically upward at 30 m/s. One second later its speed is about ____ vertically upward.

30 m/s
35 m/s
40 m/s
25 m/s
20 m/s
15 m/s
10 m/s
0 m/s

A

20 m/s

34
Q

A ball is thrown vertically upward from the surface of the earth. Consider the following quantities:
(1) the speed of the ball;

(2) the velocity of the ball;
(3) the acceleration of the ball.

Which of these is (are) zero when the ball has reached the maximum height?

1 and 2 only
1 and 3 only
1 only
2 only

A

1 and 2 only

35
Q

A ball is thrown upwards and caught once it comes back down. The speed of the ball as it returns and is caught is ___ if there is air resistance compared to if there were no air resistance.

greater
the same
double
zero
infinite
lower
none of the above

A

the same

36
Q

I drop a rock off a high cliff. How far will this rock go in 4.4 seconds, assuming that air resistance is negligible?

22 meters
49 meters
95 meters
190 meters
204 meters

A

95 meters

37
Q

I throw a rock down a high cliff with an initial velocity of 1.8 m/s. How far will this rock go in 3.8 seconds, assuming that air resistance is negligible?

64 meters
71 meters
78 meters
97 meters
142 meters

A

78 meters

38
Q

I stand at the edge of a high cliff and throw a rock upward with an initial velocity of 2.5 m/s. How far down the cliff with the rock go in 5.1 seconds, assuming that air resistance is negligible?

62 meters
115 meters
127 meters
140 meters
None of the above given.

A

115 meters

39
Q

How is the magnitudes of speed and acceleration changing as this stunt biker rolls down this quarter pipe?

Speed increases while acceleration decrease
Speed and acceleration increase
Speed and acceleration decrease
Speed decreases while acceleration increases

A

Speed increases while acceleration decrease

40
Q

Which of the following statements about 2-D kinematics is true?

ax = 0 ; ay = constant
ax = ay = constant
the x & y components of v are independent of each other
the position of x & y are always the same

A

the x & y components of v are independent of each other

41
Q

A ball is thrown straight up by a person on a moving train. To a stationary observer, the ball:

goes straight up and down.
follows a circular path.
follows a parabolic path.
goes straight forward

A

follows a parabolic path.

42
Q

Suppose you are driving a convertible with the top down. The car is moving to the right at constant velocity. You point a rifle straight up into the air and fire it. In the absence of air resistance, where would the bullet land – behind you, ahead of you, or in the barrel of the rifle?

Behind you
Ahead of you
In the barrel of the rifle

A

In the barrel of the rifle

43
Q

A ball is thrown horizontally from an initial height of 1 meter off the ground. Ignoring air resistance, what are its accelerations in the x- and y-axes?

Zero in the x and y.
Non-zero in the x and y.
Zero in the x, non-zero in the y.
Non-zero in the x, zero in the y.

A

Zero in the x, non-zero in the y.

44
Q

A student writes, “A bird that is diving for prey has a speed of − 10 m / s .” What is wrong with the student’s statement? What has the student actually described? Explain.

A

The student might be talking about the bird’s velocity, being that there is a (-) symbol in the speed.

45
Q

Acceleration is the change in velocity over time. Given this information, is acceleration a vector or a scalar quantity? Explain.

A

Since velocity is a vector, acceleration is also a vector, being that acceleration is a function of velocity.

46
Q

There is a distinction between average speed and the magnitude of average velocity. Give an example that illustrates the difference between these two quantities.

A

Since speed is a scalar, it is always positive. So the average speed will always be positive. Velocity can be positive or negative, depending on direction of travel, so the magnitude of average velocity could either be positive or negative as well.

47
Q

Does a car’s odometer measure distance or displacement? Does its speedometer measure speed or velocity?

A

Distance
Speed

48
Q

Is it possible for speed to be constant while acceleration is not zero? Give an example of such a situation.

A

It is possible. Speed is a magnitude of velocity, so though the magnitude of velocity is constant, the direction could change. This requires a non-zero acceleration.

49
Q

Is it possible for velocity to be constant while acceleration is not zero? Explain.

A

This is not possible, since acceleration changes velocity.

50
Q

Give an example in which velocity is zero yet acceleration is not.

A

At the top of trajectory for a ball thrown upward.

51
Q

If a subway train is moving to the left (has a negative velocity) and then comes to a stop, what is the direction of its acceleration? Is the acceleration positive or negative?

A

Positive

52
Q

What information do you need in order to choose which equation or equations to use to solve a problem? Explain.

A

You need to know what quantities you know and what quantities you need to find.

53
Q

What is the last thing you should do when solving a problem? Explain.

A

Check for correctness by analyzing its units and figuring out if the answer looks realistic.

54
Q

What is the acceleration of a rock thrown straight upward on the way up? At the top of its flight? On the way down?

A

Acceleration is always 9.8m/s2 downward.

55
Q

Suppose you throw a rock nearly straight up at a coconut in a palm tree, and the rock misses on the way up but hits the coconut on the way down. Neglecting air resistance, how does the speed of the rock when it hits the coconut on the way down compare with what it would have been if it had hit the coconut on the way up? Is it more likely to dislodge the coconut on the way up or down? Explain.

A

Due to the symmetry of nature, and neglecting air resistance, the rock’s speed would be the same whether you hit the coconut going up or hit it going down. Both directions of impact would probably dislodge it the same.

56
Q

If an object is thrown straight up and air resistance is negligible, then its speed when it returns to the starting point is the same as when it was released. If air resistance were not negligible, how would its speed upon return compare with its initial speed? How would the maximum height to which it rises be affected?

A

Air resistance works against an object’s motion more and more the longer it’s moving. So the speed coming down will be less than the speed going up. The maximum height will now be lower.

57
Q

(a) Explain how you can use the graph of position versus time in the graph below to describe the change in velocity over time. Identify (b) the time ( ta , tb , tc , td , or te ) at which the instantaneous velocity is greatest, (c) the time at which it is zero, and (d) the time at which it is negative.

A

Velocity is high initially and then decreases to a slight negative at the end.
At ta the instantaneous velocity is greatest.
Velocity is zero at td and is negative at te.

58
Q

(a) Sketch a graph of velocity versus time corresponding to the graph of displacement versus time given in the graph below. (b) Identify the time or times ( ta , tb , tc , etc.) at which the instantaneous velocity is greatest. (c) At which times is it zero? (d) At which times is it negative?

A

Sketch should show that the y-value of the velocity versus time graph matches the slope of the positive versus time graph at each letter on the curve.
Instantaneous velocity seems greatest at td
Instantaneous velocity is zero at tc, te, tg, and tl
Instantaneous velocity is negative at tb and tf

59
Q
A
60
Q

Consider the velocity vs. time graph of a person in an elevator shown in the figure below. Suppose the elevator is initially at rest. It then accelerates for 3 seconds, maintains that velocity for 15 seconds, then decelerates for 5 seconds until it stops. Sketch graphs of (a) position vs. time and (b) acceleration vs. time for this trip.

A

Sketch should show position graph concave up while increasing, then at t=4 it should go up linearly, then concave down while increasing starting at t=19.
Sketch should look like positive horizontal line until t=4, then zero until t=19, then negative horizontal line after t=19.

61
Q

Find the following for path A in the figure below: (a) The distance traveled. (b) The magnitude of the displacement from start to finish. (c) The displacement from start to finish.

A

7 meters
7 meters
+7 meters

62
Q

Find the following for path B in the figure below: (a) The distance traveled. (b) The magnitude of the displacement from start to finish. (c) The displacement from start to finish.

A

5 meters
5 meters
-5 meters

63
Q

Find the following for path C in the figure below: (a) The distance traveled. (b) The magnitude of the displacement from start to finish. (c) The displacement from start to finish.

A

12 meters
8 meters
+8 meters

64
Q

Find the following for path D in the figure below: (a) The distance traveled. (b) The magnitude of the displacement from start to finish. (c) The displacement from start to finish.

A

8 meters
4 meters
-4 meters

65
Q

(a) Find out Earth’s average speed relative to the Sun. (b) What is its average velocity over a period of one year?

A

About 30 km/s
About 0 km/s

66
Q

The North American and European continents are moving apart at a rate of about 3 cm/y. At this rate how long will it take them to drift 500 km farther apart than they are at present?

A

16,666,667 years

67
Q

A cheetah can accelerate from rest to a speed of 30.0 m/s in 7.00 s. What is its acceleration?

A

4.29 m/s^2

68
Q

A commuter backs her car out of her garage with an acceleration of 1.40 m/s2 . (a) How long does it take her to reach a speed of 2.00 m/s? (b) If she then brakes to a stop in 0.800 s, what is her deceleration?

A
  1. 43 s
    - 2.5 m/s2
69
Q

Assume that an intercontinental ballistic missile goes from rest to a suborbital speed of 6.50 km/s in 60.0 s (the actual speed and time are classified). What is its average acceleration in m/s2 and in multiples of g (9.80 m/s2)?

A

108 m/s2
About 11 g

70
Q

A bullet in a gun is accelerated from the firing chamber to the end of the barrel at an average rate of 6.20×105 m/s2 for 8.10×10−4 s . What is its muzzle velocity (that is, its final velocity)?

A

502.2 m/s

71
Q

At the end of a race, a runner decelerates from a velocity of 9.00 m/s at a rate of 2.00 m/s2 . (a) How far does she travel in the next 5.00 s? (b) What is her final velocity? (c) Evaluate the result. Does it make sense?

A

20 m
-1 m/s
It makes sense. Though she goes backward at the end for some odd reason, her overall progress in the 5 seconds were forward.

72
Q

Suppose that a freely falling object were somehow equipped with a speedometer. By how much would its speed reading increase with each second of fall?

A

About 9.8 m/s each second of fall.

73
Q

Suppose that the freely falling object in the preceding exercise was also equipped with an odometer. What equation is most appropriate for readings of distance fallen each second? Do the readings indicate equal distances of fall for each second? Explain.

A
74
Q

For a freely falling object dropped from rest, what is its acceleration at the end of the 5th second of fall? At the end of the 10th second? Defend your answer.

A

Always, the acceleration in free fall is g=9.8 m/s2. This doesn’t change on the surface of earth.

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