8: Motion Flashcards

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1
Q

What is the difference between a scalar and a vector?

A

A scalar has no direction - it’s just an amount of something

A vector has a magnitude and a direction

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2
Q

How do you find the resultant vector?

A

Adding two or more vectors together

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3
Q

Define speed

A

How fast something is moving, regardless of direction

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4
Q

Define displacement

A

How far an object’s travelled from its starting point in a given direction

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5
Q

Define velocity

A

The rate of change of an object’s displacement (its speed in a given direction)

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6
Q

What is instantaneous speed?

A

The speed of an object at any given moment in time

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7
Q

What is the average speed?

A

Total distance covered, over the total time elapsed

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8
Q

What is another way of saying uniform acceleration?

A

Constant

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9
Q

Define free fall

A

The motion of an object undergoing an acceleration of ‘g’. Only gravity

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10
Q

What is/are the force(s) acting on an object in free fall?

A

Weight

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11
Q

Describe the rate of free fall for different objects

A

All objects free fall at the same rate

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12
Q

What is the main uncertainty in the experiments (light gates and trapdoor) to find the value g?

A

The height h

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13
Q

What is parallax, in the context of uncertainties?

A

Systematic error due to looking at the ruler at an angle

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14
Q

In a graph of displacement against time, how can you tell that something is accelerating?

A

Graph is curved

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15
Q

What does the graph (displacement against time), look like if the object is accelerating at a uniform rate?

A

Rate of change of the gradient will be constant

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16
Q

In a displacement time graph:

If there are two objects, both accelerating, how can you tell which is accelerating more?

A

Steeper curve

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17
Q

In a displacement time graph:

If there are two objects, both accelerating, how can you tell which is accelerating less?

A

Shallower curve

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18
Q

In a displacement time graph:

How can you tell if object is decelerating?

A

The line has a deceasing gradient - so more like √x graph

19
Q

What does the gradient of a displacement time graph tell you?

A

The velocity

20
Q

How do you find the instantaneous velocity of an object, using the displacement time graph?

A

Draw a tangent and calculate the gradient

21
Q

What does the gradient of a velocity time graph show you?

A

Acceleration

22
Q

Uniform acceleration is always a [ ], on a velocity time graph

A

Straight line

23
Q

The steeper the gradient, the [ ] the acceleration

Velocity time graph

A

greater

24
Q

What is the area under a velocity time graph?

A

Displacement

25
Q

What shows that the acceleration is increasing on a velocity time graph?

A

Increasing gradient

26
Q

What shows that the acceleration is decreasing on a velocity time graph?

A

Decreasing gradient

27
Q

What do free-body force diagrams show?

A

Show a single body on it own

28
Q

Which forces are shown on a free body diagram?

A

Forces that act on the body, but not the forces it exerts on the rest of the world

29
Q

If a body is in equilibrium, the forces acting on it will be [ ]

A

Balanced

30
Q

How do you find the resultant force on a body?

A

Add the vectors (of the forces) together

31
Q

Describe the accuracy of data loggers

A

They do not have human error and can calculate the velocity and display it in real time – saving time and allowing comparisons between experiments to be easily made

32
Q

Briefly describe how iterative methods can be used for modelling displacement/velocity

A

Velocity and displacement are calculated over lots of small tiny increments/intervals of time to model their motion over a period of time

33
Q

problem with iterative models, example

A
graphs don't look realistic
they assume no change occurs within the sampled
time intervals (eg. if the calculation is applied at 5 second intervals, it is assumed that the
motion is constant between 5 and 10 seconds).
34
Q

how to improve iterative models

A

The accuracy of iterative models can

always be improved by decreasing the time interval.

35
Q

what are vectors

A

quantities with both magnitude and direction

36
Q
suvat equation not given in booklet regarding 
s
u
v
t
A
s = (u+v / 2) * t
s - displacement / m
u - initial velocity / m/s
v - final velocity / m/s
t - time / s
37
Q

overall stopping distance of a car

A

the sum of its thinking distance and braking distance

38
Q

what can affect overall stopping distance of car and how

A

the speed of the vehicle; the faster it is travelling, the greater distance it will travel in the same time it takes for the driver to react, hence producing a
larger thinking distance. The car will also need to undergo a greater braking force, resulting
in an increased braking distance.

39
Q

advantages of iterative modes

A

can be used for difficult calculus problems

40
Q

how to calculate new value of v

A

a = Δv / Δt -> Δv = aΔt

41
Q

how to calculate new value of s

A

v = Δs / Δt -> Δs = vΔt

42
Q

how to calculate value of acceleration for iteration

A
a = 9.8 - kv^-²
k = constant
43
Q

how do thinking and braking distance increase with doubling speed

A

thinking distance doubles

braking distance quadruples because of:

average speed doubling

Δv has doubled from 30 to 60, time taken for deceleration has doubled