# Forces and Motion

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• Created by: Lauran
• Created on: 17-09-13 20:15

## Velocity and Acceleration

Speed and Velocity are both measure in m/s and both simply say how fast you are going

Speed - Just how fast, no regard to direction

Velocity must have direction specified e.g 30 mph north or 20m/s, 060 degrees

Speed Distance and Time formula = S = Distance / Time

Acceleration is how quickly velocity is changing

The change in velocity can be a change in speed or a change in direction (or both)

Acceleration formula: A = Change in velocity/time taken

Unit of acceleration = m/s^2

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## D-T and V-T graphs

Distance-Time graphs:

• Flat sections are where it stopped
• The steeper the graph, the faster its going
• Downhill sections mean its going back towards starting point
• Curves represent acceleration or deceleration
• A steeping curve means it's speeding up
• A levelling curve means it's slowing down

Velocity-Time Graphs:

• Flat sections represent steady speed
• The steeper the graph, the greater the acceleration or deceleration
• Uphill sections are acceleration
• Downhill sections are deceleration
• The area under any part of the graph is equal to the distance travelled in that time interval
• A curve means changing acceleration
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## V-T graphs Extra

• Speed is found by reading the value of the velocity axis
• Distance travelled  in any time interval is equal to the area under the graph
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## Mass, Weight and Gravity

Gravity is the force of attraction between all masses:

• On the surface of a planet it makes all things accelerate toward the ground with the same acceleration e.g 10 m/s^2 on Earth
• Gives everything a weight
• Keeps planets, moons and satellites in their orbits. The orbit is a balance between the forward motion of the onject and the force of gravity pulling it inwards.

WEIGHT AND MASS ARE NOT THE SAME

Mass is the amount of matter in an object, for any object this will be the same value anywhere in the universe

Weight is caused by the pull of gravity

Weight will vary depending on where you are, mass will remain constant

Weight is measured in newtons

Mass is measured in kilograms

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## Important formula relating mass, weight and gravit

Weight = Mass x Gravitational field strength

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