On the move Flashcards

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1
Q

Define Displacement?

A

Distance in a given direction.

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2
Q

Define Speed?

A

Change of distance per unit time.

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3
Q

Define Velocity?

A

Speed in a given direction.

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4
Q

What kind of quantities are speed and distance?

A

Scalar quantities

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5
Q

What kind of quantities are velocity, displacement and acceleration?

A

Vector quantities

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6
Q

For objects that travel at constant speed, which equation can you use to calculate speed?

A
v = s/t
speed = distance/time
v = speed (m/s)
s = distance (m)
t = time (s)
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7
Q

For objects moving at a constant speed, which equation can you use to calculate its speed?

A
v = 2πr/T
speed = circumference of circle / time to move around the circle once
v = speed (m/s)
r = radius of circle (m)
T = time to move round once (s)
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8
Q

For objects moving at a changing speed, what equation can you use to calculate its average speed?

A

v = s/t
Average speed = total distance/ total time

v = average speed (m/s)
s = total distance (m)
t =(s)

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9
Q

For objects moving at a changing speed, what equation can you use to calculate its instantaneous speed at a specific point?

A

v = Δs/Δt
instantaneous speed = distance/time

v = instantaneous speed (m/s)
Δs = change in distance in a short time interval (m)
Δt = time (s)
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10
Q

On a distance-time graph, what does the height tell you?

A

The height of a distance-time graph tells you the distance of the object at the time.

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11
Q

On a distance-time graph, what does the gradient tell you?

A

The gradient of a distance-time graph tells you the speed of the object at that time.

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12
Q

On a distance-time graph, what type of graph line is produced by an object moving at a constant speed?

A

For an object moving at constant speed, a straight sloping line with a constant gradient is produced.

  • For an upwards straight sloping line, the object is moving at constant speed. A steeper line indicates that it is travelling at a higher constant speed. A shallower steep line indicates that it is travelling at a lower constant speed.
  • On a distance-time graph, there are no downwards sloping lines (no negative gradient)
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13
Q

On a distance-time graph, what type of graph line is produced by an object moving at a constantly changing speed?

*This is the same for a displacement time graph.

A

For an object moving at constantly changing speed, a curved line with a changing gradient is produced.

  • If the object is increasing in speed (accelerating), an upwards curving line with an increasing gradient is produced.
  • If the object is decreasing in speed (deccelerating), a downwards curving line with a decreasing gradient is produced.
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14
Q

How to calculate the instantaneous speed on a distance-time graph for an object that is moving at a constant speed at time t?

*This is the same for a displacement-time graph.

A

Calculate the gradient of the graph line at time t.

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15
Q

How to calculate the instantaneous speed on a distance-time graph for an object that is moving at a constantly changing speed at time t?

*This is the same for a displacement-time graph.

A

Draw a tangent to the graph line at time t, and calculating gradient of the tangent.

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16
Q

On a distance-time graph, what type of graph line is produced by an object which is stationary?

*This is the same for a displacement-time graph.

A

On a distance-time graph, for an object that is stationary, a straight horizontal line (gradient = 0) will be produced.

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17
Q

On a speed-time graph, what does the height tell you?

A

The height of a speed-time graph tells you the speed of the object at the time.

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18
Q

On a speed-time graph, what does the gradient tell you?

A

The gradient of a speed-time graph tells you the acceleration of the object at the time.

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19
Q

On a speed-time graph, what type of graph line is produced by an object moving at a constant speed?

A

On a speed-time graph, for an object that is moving at a constant, a straight horizontal line (gradient = 0) will be produced. This is the same for a velocity-time graph.

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20
Q

On a speed-time graph, what type of graph line is produced by an object moving at a constantly changing speed?

A

For an object moving at constantly changing speed, a straight sloping line with a constant gradient is produced.

  • If the object is increasing in speed (accelerating) at a constant rate, an upwards straight sloping line with a constant gradient is produced.
  • If the object is decreasing in speed (deccelerating) at a constant rate, a downwards straight sloping line with a decreasing gradient is produced.
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21
Q

On a speed-time graph, what type of graph line is produced by an object which is stationary?

A

A straight horizontal line a y = 0

This is the same for a velocity-time graph.

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22
Q

On a speed-time graph, what does the area under the graph represent?

A

The CHANGE in distance of the object.

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23
Q

On a displacement-time graph, what does the height tell you?

A

The height of a displacement-time graph tells you the displacement of the object at the time.

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24
Q

`On a displacement-time graph, what does the gradient tell you?

A

The gradient of a displacement-time graph tells you the velocity of the object at the time.

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25
Q

On a displacement-time graph, what type of graph line is produced by an object moving at a constant velocity?

A

For an object moving at constant velocity, a straight sloping line with a constant gradient is produced.

  • For an upwards straight sloping line, the object is moving at constant velocity away from the start point with a positive gradient (positive velocity)
  • For a downwards straight sloping line, the object is moving at a constant velocity returning to the start point with a negative gradient (negative velocity)

Steeper line = the higher its speed.

Positive gradient = first direction
Negative gradient = opposite direction

When the graph line returns to the starting point and continues to move in that direction, it will have a negative displacement.

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26
Q

On a velocity-time graph, what does the height tell you?

A

The height of a velocity-time graph tells you the velocity of the object at the time.

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27
Q

On a velocity-time graph, what does the gradient tell you?

A

The gradient of a velocity-time graph tells you the acceleration of the object at the time.

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28
Q

On a velocity-time graph, what type of graph line is produced by an object moving at a constantly changing speed?

A

For an object moving at constantly changing velocity, a straight sloping line with a constant gradient is produced.

  • If the object is increasing in speed (accelerating), an upwards straight sloping line with a constant gradient is produced.
  • If the object is decreasing in speed (deccelerating), a downwards straight sloping line with a decreasing gradient is produced.

However, this is only true in the positive part of the velocity-time graph (a negative and positive gradient can mean differnet in the negative part of the graph)

29
Q

What does acceleration and deceleration look like in the negative part of a velocity

This page helps a lot: https://www.pathwayz.org/Tree/Plain/MOTION+VECTORS

A

When the graph line has moved from the positive section to the negative section, it has changed direction.
Acceleration is shown by the downwards straight sloping line as the value for velocity is increasing in the negative values (e.g. -1 to -5), and thus so is acceleration. Both velocity and acceleration are negative but thats due to the change in direction (it is negative value as its travelling in the opposite direction eventhough acceleration is positive)
Deceleration is show by the upwards sloping line as the value of velocity is decreasing in the negative values (e.g. -5 to -1), and thus so is acceleration. Both velocity and decceleration are still negative but that is due to the change in direction (it is a negative value as its decelerating but also moving in an opposite direction)

30
Q

On a velocity-time graph, what does the area under the graph represent?

A

The CHANGE in displacement of the object.

31
Q

On a displacement-time graph, what does the height tell you?

A

The height of a velocity-time graph tells you the acceleration of the object at the time.

32
Q

On a velocity-time graph, what does the gradient tell you?

A

The gradient of a velocity-time graph tells you the acceleration of the object at the time.

33
Q

Define acceleration.

A

Change of velocity per unit time.

34
Q

What type of quantity is acceleration?

A

Acceleration is a vector quantity.

  • Negative values of acceleration indicate deceleration.
35
Q

What is uniform acceleration?

A

This is where the velocity of an object moving along a straight line changes at a constant rate.

Moving along a straight line = does not change direction.

36
Q

How to calculate uniform acceleration?

A
a = v-u/t
acceleration = final velocity - initial velocity / time taken
a = acceleration (ms⁻²)
v = final velocity (m/s)
u = initial velocity (m/s)
t = time taken (m/s)
37
Q

What is non-uniform acceleration?

A

This is when the direction of motion of an obejct changes or its speed changes at a varying rate.

38
Q

What does non-uniform acceleration look like on a velocity-time graph.

A
  • If the object is increasing acceleration, an upwards curving line with an increasing gradient is produced.
  • If the object is decreasing acceleration (deccelerating), a downwards curving line with a decreasing gradient is produced.
39
Q

On an acceleration-time graph, what does the height tell you?

A

The height of a acceleration-time graph tells you the acceleration of the object at the time.

40
Q

On an accleration-time graph, what does the area under the graph tell you?

A

The CHANGE in velocity of an object.

e.g. +8m/s

41
Q

On an acceleration-time graph, how do you know if an object is increasing or decreasing acceleration uniformly?

A

For the positive part of the graph:

  • If an object is increasing in acceleration uniformly, a upwards straight sloping line with a constant gradient is produced.
  • If the object is decreasing in acceleration (not deccelerating, but rather stop increasing speed and reach constant velocity), a downwards straight sloping line with a decreasing gradient is produced.

For the negative part of the graph:
- If an object is traveling in the direction that is considered negative then a negative acceleration means that the object is getting faster. But if an object is traveling in the positive direction then a negative acceleration would mean that it is slowing down

Is stop increasing speed deceleration?
Or is decreasing speed, deceleration
What is deceleration and acceleration on the positiive and negative side of the graph?

42
Q

On an acceleration-time graph, what type of graph line is produced by an object which is stationary?

A

You can only indicate velocity is constant on an acceleration-time graph by having the graph be a flat line along the time axis so the acceleration is 0. On the graph you can’t tell if the constant velocity is 0 or 1,000 m/s.

43
Q

If a question on what is the maximum speed obtained by the vehicle, what do you have to look at?

A

You have to look at when acceleration = 0, no longer accelerating.

44
Q

For a velocity-time graph, how do you calculate the acceleration at any point of an object, which is accelerating non-uniformly?

A

Draw a tangent to the specific point, and calculate the gradient of the tangent.

45
Q

What are the four main equations that are used to solve problems involving uniform acceleration?

Uniform acceleration = acceleration does not change.

A
v = u + at
s = ut + ½at²
s = ½(u+v)t
v² = u² + 2as

When asked questions invovling these, write duvat down the side of your page

46
Q

What is free-fall?

A

Free fall is defined as the motion of an object undergoing an acceleration due to gravity and thus the only force acting on it is weight (and no other forces).

Objects can have an initial velocity in any direction and still undergo free fall as long as the force providing the initial velocity is no longer acting.

47
Q

What is the value for the “acceleration of free fall”?

A

9.8ms⁻²

48
Q

Because all free-falling objects have the same acceleration acting on it so….

A

…if dropped at the same time, reaches the ground at the same time.

49
Q

Draw the displacement-time graph and distance-time grap, for a ball being thrown directly upwards and then returning to the thrower?

A

PAGE 128

50
Q

Describe the velocity of the ball thats being thrown and returns, using the displacement graph.

A
  • Immediately after leaving the throwers hand, the velocity is positive and large, so the gradient is positive and large
  • As the ball rises, its velocity decreases, so its gradient decreases.
  • At the maximum height, its velocity is zero so the gradient is zero.
  • As the ball descends, its velocity becomes increasingly negative, corresponding to the increasing speed in the negative speed in the downward direction. So the gradient becomes increasingly negative.
51
Q

Draw the velocity time graph for throwing the ball, and when it returns?

A

Figure 3 on pg129

52
Q

Draw a velocity-time graph of when a ball is dropped and bounces up and down? Label, when its falling, bouncing and rising, where its peak is also.

A

Figure 4 on pg129, BUT EXTEND IT.

This is if elastic collision occurred. Try drawing inelasic collision for a bouncing ball.

53
Q

An object is released from rest, falling and then hitting a bed of sand. Why must two suvat calculation steps be done?

A

This is because the motion is in two stages, of which both stages have a different acceleration:

1) falling motion diue to gravity where acceleration is = 9.81ms⁻²
2) deceleration in the sand, where the initial velocity is the velocity of the object just before impact.

54
Q

What is a projectile?

A

A projectile is anything acted upon only by the force of gravity.

55
Q

Three key principle of projectile motion?

A

1) Acceleration of the object is always equal to 9.81 and always acts downwards as teh force of gravity acts vertically downwards. Thus the acceleration affects only the vertical motion of the object.
2) The horizontal velocity of the object is constant because the acceleration of the object does not have a horizontal component.
3) The motions in the horizontal and vertical directions are independant of each other.

56
Q

To calculate vertical motion in the topic of projectile motion what do we need to use?

A

We need to use SUVAT equations because the object has constant acceleration under gravity.

57
Q

If an object is thrown from a cliff…

A

…it has an initial projection which is horizontal.

58
Q

If an object has a horizontal projection, what does this mean?

A

Its path through the air becomes steeper and steeper as it drops.
The faster it is projected, the further away it will fall.
The time taken for it to fall does not depend on how fast it is projected..

59
Q

If two balls are released at the same time, such that one ball is dropped vertically and the other is projected horizontally, they both hit the floor vertically. Why?

A

This is because:

1) Both are pulled to the ground by the force of gravity.
2) This means both of them have a vertically downward acceleration of 9.81ms⁻².
3) As the vertical motion is independant of the horizontal motion, as they both have the same vertical motion, their difference in horizontal motion does not affect the time it takes to reach the ground (which is affected by vertical motion).

60
Q

What shaped path does a object projected horizontally have?

A

A parabolic path.

61
Q

How to find the displacement of its horizontal motion, x? i.e. how far it goes horizontally?

A

x = Ut
horizontal displacement = initial velocity x time after projection

x = horizontal displacement (m)
U = initial velocity (m/s)
t = time after projection (s)
62
Q

How to find the displacement of its vertical motion, y? i.e. how far it goes vertically

A

y = ½gt²
vertical displacment = gravity x time after projection

y = vertical dispalcement
g = gravity (ms⁻²)
t = time after projection (s)
63
Q

What opposing force acts on projectiles moving through the air?

A

Drag force due to air resistance.

64
Q

How does the drag force affect the project?

A
  • Acts in the opposite direction to the motion of the projectile and it increases as the speed of the projectile increases.
  • Has a horizontal componenet that reduces the horizontal velocity of the projectile and its range.
  • Reduces the maximum height of the projectile, if its initial direction is above the horizontal and make its descent steeper than its ascent.
65
Q

Draw a projectile, with and without air resistance?

A

Search ‘projectile with air resistance’ on google or look at page 134 figure 3.

66
Q

How may a projectile’s shape affect its path?

A

Depending on the shape, the projectile might cause a lift force. This happens when the shape of the projectile, cause the air to flow faster over the top of the object than underneath so the pressure above is less than below and this pressure difference causes a lift force on the object.

67
Q

If a projectile is first projected at an angle, you start with both a horizontal and vertical velocity. How do you these type of calculation?

A

1) Resolve the initial velocity into horizontal velocity(by doing U x cosθ) and vertical velocity(U x sinθ)
2) Use the vertical velocity to work out how long it takes to reach its highest point (use SUVAT equation, initial velocity is the calculated vertical velocity, final velocity which is 0, at the top, and acceleration which -9.81ms⁻²). Doubling this time tells you how long it takes to reach its highest point and drop back to the height it was thrown from. At this point, it has the same velocity as the initial velocity but negative. If the continue to travel further down, you will need to use this information to calculate the final section.
3) Use the horizontal component to work out how far it goes horizontally while its in the air (using v = s/t)

θ = this is the angle from the horizontal
https://www.youtube.com/watch?v=1n_gBsoy-mc

68
Q

To calculate how far the projectile reach horizontally, why can we use v = st?

A

This is because horizontal acceleration is 0, so horizontal speed (that we calculated) remains constant and thus we can use v = st.