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Physics 21st Century > Explaining motion > Flashcards

Flashcards in Explaining motion Deck (83)
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1

What does the speed of an object tell us?

How far it will travel in a certain time

2

How do you calculate speed?

Speed (m/s) = distance travelled (m)/time(s)

3

If the object is not travelling at a constant speed what does distance/time give us?

The average speed.

4

How many seconds in a minute?

60

5

How many seconds in an hour?

3600

6

If the question gives time in hours, and you need to calculate speed in m/s, what can you do?

Convert hours into seconds.

7

What does average speed over a very short time interval give you?

A value that is close to instantaneous speed (though it will still be an average over that small time interval)

8

What is the displacement of an object?

The distance from the start - so earth travels a long way in a year, but the displacement (seen from the sun) is zero.

9

Why is displacement a vector?

It has size (magnitude) and direction.

10

What is velocity?

Speed in a certain direction.

11

Why is velocity a vector?

It has magnitude and direction.

12

When plotting a distance time graph, where does time go?

On the X axis

13

When plotting a distance time graph, where does distance go?

On the Y axis.

14

What does a horizontal line on a distance time graph tell you?

The object being tracked is not moving.

15

What is horizontal?

Parallel to the floor ... the X axis on a graph

16

What is vertical?

Sticking straight up into the air... the Y axis on a graph.

17

On a distance time graph, what is the gradient equal to?

The speed, but only if you have time on the X axis.

18

On a distance time graph, what does a curved line show?

The speed is changing

19

On a distance time graph what does a steeper line mean?

The object being tracked is moving faster.

20

On a distance time graph what would a vertical line mean?

The object has moved an infinite amount of distance in zero time.

21

What is a displacement time graph?

A way of showing a return journey, where displacement goes to 0 when the object returns.

22

What does the graph going below the X axis mean on a displacement time graph?

The object went past the starting point and kept going, it is now behind the position that it started at.

23

What is acceleration?

The rate at which an object changes velocity

24

If an object is slowing down, what is it doing?

Showing negative acceleration. Can be called retardation or deceleration.

25

What is the unit of acceleration?

metres per second per second - m/s^2

26

What is a car doing when going round the corner at a constant speed?

Accelerating. It is changing direction, this is still acceleration

27

On a speed-time graph, what goes on the X axis?

Time

28

On a speed-time graph, what goes on the Y axis?

Speed

29

On a speed time graph, what does a horizontal line mean?

The object is going at constant speed.

30

On a speed time graph, what does it mean if the graph is on the X axis?

The object is not moving (stationary)