# Revision (physics 1)

distance-time graphs and velocity and acceleration.

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What is a distance-time graph?
A distance-time graph shows the distance of a body from a starting point (usually on the y-axis) against time taken (on the x-axis).
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What does the gradient on a distance-time graph represent?
The gradient is the object’s speed. If an object is stationary the line on the distance-time graph is horizontal, so the gradient is nothing. If it’s moving at a constant speed then the line would be a straight line sloping upwards.
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What is the equation need to calculate the speed?
Speed in metres per second, m/s =distance travelled in metres, m divided by time taken in seconds, s. This equation can be re-arranged to calculate the time taken or distance travelled.
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What is the difference between speed and velocity?
Speed is a scalar quantity (non-directional - has a magnitude) and velocity is a vector quantity (has a direction + a magnitude). The difference between the two is that one has a direction, the other doesn’t. (velocity IS speed in a given direction).
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What is the equation need to work out acceleration?
Acceleration, m/s² = change in velocity, m/s (final velocity, stood for by v, minus initial velocity stood for by u) divided by time taken for change (between the two velocities). Equation can be re-arranged to show v = u + at.
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What is deceleration?
When the value calculated for acceleration is negative, it’s called deceleration. Deceleration is the same as a negative acceleration.
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## Other cards in this set

### Card 2

#### Front

What does the gradient on a distance-time graph represent?

#### Back

The gradient is the object’s speed. If an object is stationary the line on the distance-time graph is horizontal, so the gradient is nothing. If it’s moving at a constant speed then the line would be a straight line sloping upwards.

### Card 3

#### Front

What is the equation need to calculate the speed?

### Card 4

#### Front

What is the difference between speed and velocity?

### Card 5

#### Front

What is the equation need to work out acceleration?