Whole standard grade Physics transport topic!

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## Speed

Speed is how fast and object is travelling and is always equal to the distance travelled in one second.

To measure the average speed =  d=v/t

Average speed is the steady speed of and object over a period of time.

Instantaneous speed is the speed of an object at a particullar time (instant)

To measure the instantaneous speed you use a light gate.

When the moving object breaks the beam of light, the timer starts then as soon as the beam is remade the timer stops and the accurate speed can be calculated.

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## Acceleration

Acceleration= the rate of change of speed.

If an object is changing its speed velocity it is accelerating.

To calculate acceleration= change in velocity/timetaken

a= v-u/t

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## Speed Time Graphs

In a speed time graph:

• Horizontal line= constant speed
• Straight line sloping upwards= constant acceleration
• Straight line sloping downwards= constant deceleration

The area under a speed time graph shows the distance an object has travelled.

Average speed= area under the graph/ total time taken

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## Forces

A force applied on an object has the ability to change:

• shape
• speed
• direction of movement

of an object.

We can measure the size of a force using a Newton Balance.

Mass= the amount of matter there is in an object(kg)

Gravitational field strength= every kg of mass has a weight of 10N on earth g=w/m

Weight= is the earths pull on an object and depends on the gravitational field strength. w=mxg

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## The Force of friction

Friction opposes the motion of an object. Whenever an object moves friction is present.

Streamlined objects are shaped so it cuts through the air with less resistance.

in order to stop a vehicle a braking force is applied to it.

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## Newton's Laws

If there is a balanced force then there will be no movement, there is only movement with an unbalanced force.

1st Law: An object will remain at rest or will remain at constant speed in a straight line unless acted on by an unbalanced force.

Larger force = Larger acceleration

Smaller mass= Larger acceleration

2nd Law: The acceleration of an object varies directly with unbalanced force and inversely with its mass.

Unbalance Force= Mass x Acceleration

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## Work, Energy and Power

Energy Transformations-

• Car accelerating= Potential energy--- Kinetic Energy
• Car moving at constant speed+ Potential----- Heat energy
• Car Breaking= Kinetic-----potential energy+heat
• Car moving uphill at constant= Kinetic----potential energy+heat
• Car rolling down hill= potential energy ----- kinetic energy

Work done= Force x Distance Moved

Kinetic Energy= half x mass x velocity(squared)

Gravitational Potential Energy= mass x gravitational pull x height

Power= work done/ time taken

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