motion ,speed , distance and displacement
Answers
Speed, velocity, scalars and vectors
Forces can change the position, shape or motion of an object. They can make objects speed up, slow down or change direction. It is the direction of movement that shows the difference between a scalar and a vector measurement – this is the difference between the speed of an object and its velocity.
Speed
Speed is a measure of how fast something is travelling. It is the distance travelled in unit time. Speed is measured in m/s or km/h (or mph in UK cars).
Speed, or distance and time can be calculated using the DST triangle.
A formula triangle showing that Distance is equal to Speed multiplied by Time.
Cover the letter you want to find to get the formula you need.
D = S × T
S = D ÷ T
T = D ÷ S
Question
If a car travels 24 m in 2 seconds, what is its speed?
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Velocity
The only difference between velocity and speed is that velocity has a direction.
Displacement is the distance moved in a straight line, or a given direction from the starting point.
Question
If a car travels 24 m east in 3 seconds, what is its velocity?
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Question
An aerial view of the floorplan of a house. The house is square, and each side measures 10 metres. The upper right corner is labelled 'Start/Finish'.
You walk all the way around the house in the diagram in 20 seconds.
a) What is your speed?
b) What is your velocity?
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Scalars and vectors
Measurements that have magnitude (size) only are called scalar measurements.
Measurements that have size and direction are called vector measurements.
Speed is a scalar measurement - direction is not important. Velocity is a vector measurement - direction is important.
Some scalar measurements you are likely to use in Physics are:
distance
speed
time
Some vector measurements you are likely to use in Physics are:
displacement
velocity
acceleration
force
momentum
Question
Find the distance travelled by a runner moving at 9 m/s for 4 seconds.
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Question
Find the time taken to cover 256 m at a speed of 8 m/s.
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Question
Find the velocity of a train if it covers 1,000 metres in a south direction in 25 seconds.