Chapter 3.1 - Motion Flashcards

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1
Q

Instantaneous Speed

A

The speed at a certain time

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2
Q

Displacement

A

A vector quantity that represents how far an object has travelled from its starting point in a given direction

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3
Q

Average Speed

A

Distance / Time

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4
Q

Average Velocity

A

Displacement / Time

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5
Q

Distance

A

A scalar quantity that shows how far something travelled along a certain route

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6
Q

Velocity

A

A vector quantity that shows rate of change of displacement

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7
Q

Acceleration

A

A vector quantity, the rate of change of velocity

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8
Q

Gradient of displacement-time graph

A

Velocity

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9
Q

Gradient of velocity-time graph

A

Acceleration

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10
Q

Area under velocity-time graph

A

Displacement

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11
Q

The 4 SUVAT equations

A
v = u + at
s = 0.5(u + v)t
s = ut + 0.5at^2
v^2 = u^2 + 2as
(s = vt - 0.5at^2)
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12
Q

value of g

A

9.81

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13
Q

Acceleration of a body in free fall

A

-g

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14
Q

Is horizontal velocity independent of vertical

A

yes

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15
Q

The two types of approaches for measuring g

A

Direct e.g. timing a falling ball

Indirect e.g. timing a pendulum

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16
Q

Describe the experiment to measure g (trapdoor)

A
  • Set up a steel ball supported by an electromagnet
  • Turn of current so ball is released and clock started
  • When ball hits trap door a connection is broken and timer is stopped
  • We now have u, s, t and want to find a so we can rearrange a SUVAT
  • Can plot a graph with different values of s (and t)
17
Q

Potential sources of error for g trapdoor experiment (3)

A
  • Electromagnet current too high can cause delay
  • If distance is too large air resistance might have a noticeable effect
  • Measurement of distance
18
Q

Experiment to measure g (light gates)

A
  • A piece of card is dropped from a certain height above a light gate
  • Light gate and data logger calculate v, u = 0, s = measured so a can be calculated
  • A graph of v^2 against s can be plotted with the gradient being 2g
19
Q

Assumptions made by light gate g experiment

A

The cards velocity is constant as it travels through the gate

20
Q

Thinking distance

A

Distance a car travels between driver seeing hazard and applying brakes

21
Q

Braking Distance

A

Distance between applying brakes and coming to rest

22
Q

Stopping distance

A

thinking distance + braking distance

23
Q

Factors that increase thinking distance (5)

A
  • high speed
  • tiredness
  • alcohol / drugs
  • Distractions
  • Age
24
Q

Factors that increase braking distance (5)

A
  • high speed
  • poor road conditions
  • poor brake conditions
  • poor tyre conditions
  • mass of car
25
Q

Equation for thinking distance

A

reaction time * speed

26
Q

Relationship between braking distance and speed

A

squared

27
Q

Why is braking distance proportional to speed squared

A

Because brakes constantly do work against the car, and the total energy is 0.5mv^2

28
Q

Equipment used to investigate motion and collisions of objects

A
  • Trolleys, light gates, data loggers

- Video recording and analysing frame by frame