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42 Cards in this Set
- Front
- Back
What is the difference between a vector and a scalar?
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A vector has magnitude (size) and direction whereas a scalar has size only.
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What is the difference between speed and velocity?
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Speed is a scalar and velocity is a vector - speed in a particular direction
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What words should we use when describing motion?
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Speed, direction, constant (no acceleration or changing speed and/or direction - acceleration,
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What can help us to describe the movement of a body?
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Graphs: these may be distance-time graphs or velocity-time graphs.
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What does the slope (gradient) of a distance-time graph represent?
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Speed
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What is the velocity of a body?
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It is its speed in a given direction.
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What is the acceleration of a body?
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It is the rate of change of velocity (change in velocity divided by time).
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What is the unit of velocity?
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Metres per second (m/s)
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What is the S.I. unit of acceleration?
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Metres per second squared
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What is the S.I. unit of distance?
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metres (m)
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What is the S.I. unit of time?
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second (s)
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How can you find acceleration from a velocity/time graph?
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The slope (gradient) of a velocity-time graph represents acceleration.
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How can you find distance travelled from a velocity/time graph?
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The area under a velocity-time graph represents distance travelled.
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How can you change the speed of a body
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Make a force act on it.
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What is acceleration evidence of?
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A 'net force' or 'unbalanced forces' acting on a body.
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What happens whenever two bodies interact?
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The forces they exert on each other are equal and
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What is a resultant force?
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A number of forces acting on a body may be replaced by a single force which has the same effect on the body as the original forces all acting together.
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If the resultant force acting on a stationary body is zero, what will the body do?
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The body will remain stationary.
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If the resultant force acting on a stationary body is not zero, what will the body do?
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The body will accelerate in the direction of the resultant force.
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If the resultant force acting on a moving body is zero the body, what will the body do?
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It will continue to move at the same speed and in the same direction.
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If the resultant force acting on a moving body is not zero, what will the body do?
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The body will accelerate in the direction of the resultant force.
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What does it mean when a vehicle travels at a steady speed?
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It means that the frictional forces balance the driving force.
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How is braking force related to stopping distance?
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The greater the speed of a vehicle the greater the braking force needed to stop it in a certain distance.
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What two parts make up the stopping distance of a vehicle?
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The stopping distance of a vehicle depends on the distance the vehicle travels during the driver’s reaction time and the distance it travels under the braking force.
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What can affect a driver’s reaction time?
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Tiredness, drugs and alcohol.
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What can affect vehicle’s braking distance?
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Adverse road and weather conditions and poor condition of the vehicle.
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How does speed through a fluid affect friction?
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The faster a body moves through a fluid the greater the frictional force which acts on it.
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What is terminal velocity?
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The speed reached when a body falls through a fluid and weight equals drag.
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How is kinetic energy related to speed?
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The faster the speed the higher the kinetic energy.
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What happens when a force causes a body to move through a distance?
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Energy is transferred and work is done.
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What is 'work'?
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Work is done whenever energy is transferred - it is the result of energy transfer.
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What energy transfer occurs when work done against frictional forces?
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Kinetic energy is transformed into heat.
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When work is done on the object to change its shape how can that energy be stored?
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As elastic potential energy.
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What does kinetic energy of a body depend on?
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The kinetic energy of a body depends on its mass and its speed.
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What two things increase with speed?
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The faster a body is moving the more kinetic energy and momentum is has.
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When working out what happens to bodies as a result of explosions or collisions; which is the most useful to think about, momentum or energy change?
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Momentum.
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What is the law of conservation of momentum?
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The sum of the momentum of bodies before an event is equal to the sum of the momentum after the event as long as no external forces act.
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Is momentum a scalar or a vector?
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A vector - momentum has both magnitude and direction.
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What causes a change in momentum?
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When a force acts on a body that is moving, or able to move, a change in momentum occurs.
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What happens when a change in momentum of a body occurs?
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Acceleration
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What is the impulse of a force?
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The force multiplied by the time it acts.
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What is impulse equal to?
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The change in momentum it produces.
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