# Shared Flashcard Set

## Details

AQA Physics module 2 keywords
Keywords that you must understand and use when answering questions in this examination.
15
Physics
05/19/2009

Term
 Speed
Definition
 How far you travel in a certain period of time. In Physics we usually measure the distance travelled in metres per second.Speed = distance / time
Term
 Velocity
Definition
 Velocity is a speed and direction.
Term
 Acceleration
Definition
 Acceleration describes how the speed of an object changes in fixed amount of time. In Physics we measure the change in speed in metre per second per second or m/s2.
Term
Definition
 The steepness of a slope of a line graph. On a distance-time graph the gradient is equal to the speed of the object. On a speed-time grpah the gradient is equal to the acceleration of the object.
Term
 Balanced forces.
Definition
 The forces on an object cancel each other out so the resultant force is zero.  The forces are usually the same size but in opposite directions.
Term
 Unbalanced forces
Definition
 If the forces on an object are unbalanced then the resultant force is not zero.   The forces acting on an object are not the same size and/or not in opposite directions.
Term
 Resultant force
Definition
 Forces in the same direction add together. Forces in the opposite direction take away. The net single force is called the resultant force.
Term
 Stopping distance
Definition
 The stoppng distance is the distance a vehicle travels from when the driver sees the incident until the car comes to a stop. The stopping distance can be divided into two parts, the thinking distance and the breaking distance.
Term
 Thinking distance
Definition
 The distance a vehicle travels before the driver reacts to the incident. This depends on the drivers reaction time (affected by tiredness, talking on mobile phones, drinking alcohol for example) and the speed of the vehicle.
Term
 Braking distance
Definition
 The distance the vehicle travels once the brakes are applied until it comes to a stop. This is affected by friction (tyres, ground or brakes), speed of the vehicle and the mass of the vehicle.
Term
 Kinetic energy
Definition
 Kinetic energy describes the energy of a moving object. Kinetic energy is proprtional to mass (whatever happens to one will happen to the other.  If you double one then you double the other) However kinetic energy is proportional to the speed of the object squared.  (if you double the speed the kinetic energy would quadruple!)
Term
 Work
Definition
 Energy cannot be made or destroyed it can only be converted. When energy is converted from one type to another, scientists say that work has been done. Work = Amount of energy converted.
Term
 Momentum
Definition
 Momentum is another way to describe the motion of an object which is particularly useful for understanding the effects of collisions. Momentum is measured in kgm/s.
Term
 Change in momentum
Definition
 The rate at which momentum changes describes the force needed to cause it. If the change in momentum of an object happens quickly (small amount of time) then the force to cause the change in momentum is very big. If the change in momentum of an object happens slowly (large amount of time) then the force to cause the change in momentum is very small.
Term
 Conservation of momentum
Definition
 Momentum is not lost or made unless a force acts on the object. Total momentum before = Total momentum after
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