Deceleration
If the brakes of a bicycle or car are pressed the velocity of the vehicle decreases The bicycle or car is then said to have a decclcration.
Uniform deceleration means that the velocity decreases by equal amounts in cqual times, no matter how small the times may be.
deceleration =velocity change/time taken
but as the velocity decreases with time it can be considered as negative acceleration.
Suppose a train slows uniformly from 98 to 48 km/h in 10s. Then
deceleration=(98-48) km/h÷10s =5 km/h per s
So 2s after the velocity of 48 km/h is reached, the velocity decreases by 5 x2 or 10 km/h. The velocity is then 48-10 km/h or 38 km/h. It can be seen that 9.6s after 48 km/h is reached the train comes to rest.
If an object is thrown up into the air, it undergoes a uniform deceleration of
about 10 m/s² due to gravitational attraction; that is, its velocity decreases by 10 m/s for each second it rises.
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