P2A

Notes on physics

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  • Created by: mellow
  • Created on: 24-05-11 20:16

velocity time graphs

Velocity-graphs

Velocity is speed in a given direction.                 Graph of a cyclist journey

(http://www.edu.xunta.es/ftpserver/portal/S_EUROPEAS/FQ/1stBAC_archivos/Exams_archivos/image003.gif)

- Slope A: Positive acceleration

- Horisontal B: Constant velocity

- Slope C: Postitive acceleration

What is the acceleration during part C?

Acceleration=Change in velocity/time taken for change

Acceleration= 80-40/60-50 = 40/10=4m/s positive acceleration

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Forces

(http://www.bbc.co.uk/schools/gcsebitesize/science/images/carforces.jpg)Forces

The bigger the arrow the larger the force that is being excerted.

Since the driving force's arrow is bigger than air resistance the car is accelerating.

 (http://thumbs.dreamstime.com/thumb_237/1203022004s7xQp1.jpg)

If the two forces are balanced then the car would be stationary. Think of two teams pulling a rope in a game of tug of war, if both of the forces they exert are the same then they are all stationary, no one wins as the rope dosen't move.

The bigger the force the bigger the acceleration.

The bigger the mass, the smaller the acceleration.

In a car, braking increases the frictional forces, reducing the speed (negative acceleration.

(http://www.cyberphysics.pwp.blueyonder.co.uk/graphics/diagrams/skydiver4.gif)

A parchutist falling at conatant velocity his: his weight acting downwards balances the air resistance acting upwards.

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