Flashcards in 3.1 Motion Deck (28):

1

## Instantaneous Speed

### The speed at a certain time

2

## Displacement

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

3

## Average Speed

### Distance / Time

4

## Average Velocity

### Displacement / Time

5

## Distance

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

6

## Velocity

### A vector quantity that shows rate of change of displacement

7

## Acceleration

### A vector quantity, the rate of change of velocity

8

## Gradient of displacement-time graph

### Velocity

9

## Gradient of velocity-time graph

### Acceleration

10

## Area under velocity-time graph

### Displacement

11

## The 4 SUVAT equations

###
v = u + at

s = 0.5(u + v)t

s = ut + 0.5at^2

v^2 = u^2 + 2as

(s = vt - 0.5at^2)

12

## value of g

### 9.81

13

## Acceleration of a body in free fall

### -g

14

## Is horizontal velocity independent of vertical

### yes

15

## The two types of approaches for measuring g

###
Direct e.g. timing a falling ball

Indirect e.g. timing a pendulum

16

## Describe the experiment to measure g (trapdoor)

###
- 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

## Potential sources of error for g trapdoor experiment (3)

###
- Electromagnet current too high can cause delay

- If distance is too large air resistance might have a noticeable effect

- Measurement of distance

18

## Experiment to measure g (light gates)

###
- 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

## Assumptions made by light gate g experiment

###
The cards velocity is constant as it travels through the gate

20

## Thinking distance

###
Distance a car travels between driver seeing hazard and applying brakes

21

## Braking Distance

###
Distance between applying brakes and coming to rest

22

## Stopping distance

### thinking distance + braking distance

23

## Factors that increase thinking distance (5)

###
- high speed

- tiredness

- alcohol / drugs

- Distractions

- Age

24

## Factors that increase braking distance (5)

###
- 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