Chapter 3.1 - Motion Flashcards

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
Equation for thinking distance
reaction time * speed
26
Relationship between braking distance and speed
squared
27
Why is braking distance proportional to speed squared
Because brakes constantly do work against the car, and the total energy is 0.5mv^2
28
Equipment used to investigate motion and collisions of objects
- Trolleys, light gates, data loggers | - Video recording and analysing frame by frame