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0

How to calculate speed?

Total distance / time taken
Unit: m/s

1

Interpret speed time graph

Area underneath = distance travelled
Flat line = constant speed
Straight line going up/down: constant acceleration or deceleration
Acceleration not constant -> curve

2

Interpret distance- time graph

The slope= speed
The steeper the slope the grater the speed
Flat line= stop
Curve up= slowing down and vice versa

3

What is acceleration

The change of velocity per second
Unit: m/s2

4

How to calculate acceleration

Change in velocity / time taken for the change

5

Acceleration of free fall for a body near to the earth?

Constant acceleration

6

What is velocity?

Speed in given direction

7

What happen to the motion of a falling body

Object are slow down by air resistance
Air resistance gets bigger as accelerate
Once air resistance = force of gravity, the object has reached terminal velocity
Object stay at a constant velocity

8

What is terminal velocity

When a free falling body air resistance force and gravity force is equal and the object will stay at a constant velocity.

9

What is mass?

A measure of the amount of matters a body contains

10

What is inertia

An object's resistance to a change in its motion
The greater the mass, the more inertia it has

11

How to calculate weight?

1kg = 10N

12

What is density

How tightly packed matter is and the amount of mass in a given space

13

How to calculate density?

Mass/ volume

14

What is the density of water and when does an object sink in water?

Density of water= 1g/cm3
Density of object > density of water => sink

15

How to measure volume of a irregular object?

Put the object into measuring cylinder with water. When you add the object, it displaces the waters, making the water level rises
The rise= volume of object

16

What is the effect of force?

Change in size, shape, speed or direction

17

What is elastic

When an object regains its original shape when the force that deform it are removed -> it is elastic

18

What is elastics limit?

The limit to which an object can be stretched without being permanently extended

19

What is hooke's law?

F=kx
K is spring constant, extension is directly proportional to the weight

20

What is the name when the force no longer directly proportional to the extension?

Limit of proportionality

21

What is resultant force?

A single force that has the same effect as all the forces acting on the object

22

What happen when resultant force =0

The object remain at rest if it was already at rest
Continue to move at the same speed and in the same direction if it was already moving

23

How to calculate force?

Mass x acceleration

24

Describe circular motion

An object moving around a circular path is acted by a resultant force which is directed towards the cent of the circle
The resultant force is called the centripetal force

25

What is moment?

Turning force

26

What is moment of the force

The turning effect of the force
Measured in Newton
Can be either clockwise or anticlockwise

27

How to calculate moment?

Force x perpendicular distance to pivot
Unit Nm
F x d

28

Describe an object in equilibrium

No resultant force on it
No resultant turning force on it

29

Describe the principal of moment

For an object in equilibrium, the sum of all the clockwise moment about any point = the sum of all anticlockwise moments about that point