OCR Physics - P2 - MOTION

GCSE Physics P2 is made up of: "Motion" - "Speeding up and slowing down" and "work, energy and momentum". These revision cards are for "motion"

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Distance-time graphs

They help us describe the motion of a body.

They show the distance of a body from a starting point (y-axis) against time taken (x-axis).

The steeper the line, the greater the speed it represents. (the slope represents speed).

The speed of a body is the dista.nce travelled each second. Calculated using:-
Speed (m/s) = distance travelled (m) ÷ time taken (s)

*note* Always label axes on the graph with a quantity and a unit.

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Velocity and acceleration

The velocity of a body is its speed in a given direction. If it changes direction, it changes velocity, regardless of its speed.

Acceleration (m/s²) = change in velocity ÷ time taken for the change.

If the acceleration is a negative number, the body is decelerating (slowing down)

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Velocity-time graphs

They show the velocity of a body (y-axis) against time taken (x-axis).

The slope of a line on a velocity-time graph represents acceleration
The steeper the slope, the greater the acceleration
If the slope is negative, the body is decelerating (we learnt all of this before...)
The area under the line on a velocity-time graph represents the distance travelled in a given time
The bigger the area, the greater the distance travelled

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Using graphs

If you calculate the slope of the line on a distance-time graph for an object, the answer you obtain will be the speed of the object.

If you calculate the slope of the line on a velocity-time graph for an object, the answer you obtain will be the acceleration of the body.

Calculating the area under the line on a velocity-time graph between two times gives the distance travelled between those times

10| / /
08| / |
06| / |
04| / Straight Line! |
02| / | Slope= 10 ÷ 20 = 0.5 m/s²
00|/________________ |__
0 4 8 12 16 20

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