Physics AS Mechanics Unit 2

Set of revision cards containing definitions and equations included in specification.

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Moment

Force x perpendicular distance

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A Vector is...

...A physical quantity with both magnitude and direction

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A Scalar is...

...A physical quantity with magnitude only

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Velocity

Change in distance / Change in time

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Acceleration

Change in velocity / Change in time

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Equations of Motion

v = u + at

2s = (u+v) x t

v^2 = u^2 + 2as

s = ut + 0.5 x a x t^2

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Force

Mass x Acceleration

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Work Done (Energy Transferred)

Force x distance moved

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Kinetic Energy

0.5 x m x v^2

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Gravitational Potential Energy (GPE)

m x g x (change in h)

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Elastic Potential Energy

0.5 x k x e^2

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Work done to overcome friction

mgh - 0.5 x m x v^2

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Power

The rate of transfer of energy

Measured in Watts. 

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Equations of Power

Energy transferred / time

Work done / time

Force x Velocity 

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The efficiency of a machine..

useful energy transferred by the machine / total energy supplied into the machine

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Principle of Conservation of Energy

Energy cannot be destroyed or created, it can only be turned into different forms.

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Joules (J)

Energy is measured in Joules.

One Joule is defined as the energy required to move an object of weight 1N through a distance of 1m. 

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Watt (W)

Power is measured in Watts.

One Watt is defined as a rate of transfer of energy equal to 1 Joule per second. 

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Components of Force

Horizontal = F cos theta

Vertical = F sin theta 

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The Principle of Moments

Sum of Clockwise moments = Sum of Anti-clockwise moments

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Distance travelled

Speed x time

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Distance travelled

Area under the line of a speed-time graph

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Projectile Motion

Horizontal component = initial speed x time

Vertical Component = 0.5 x gravity x time^2 

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Newton's Laws

First Law

Objects either stay at rest or remain in uniform motion in the same direction unless acted on by an external force

Second Law 

Force = mass x acceleration

Third Law (Law of Inertia)

Weight = mass x gravity 

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Thinking Distance

The distance travelled in the time it takes the driver to react to the hazard.

Speed x reaction time 

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Braking Distance

The distance it takes for the car to stop completely once the driver has reacted.

v^2 / 2a 

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Stopping Distance

Thinking distance + Braking Distance

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What factors might affect stopping distance?

  • Greasy/icy road
  • Medication/Drugs
  • Alcohol
  • Road conditions
  • Weather
  • Tyre conditions 
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What safety features does a car have, and what do

  • Vehicle Bumpers
  • Airbags
  • Collapsible Steering Wheel
  • Crumple zones
  • Seat Belts

They all increase impact time, which reduces impact force, which lessens the force of the crash on the driver.

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