ACCELERATION

All these are examples of CHANGES in the velocity of an object. It's actually a good thing to have a car that can change its velocity quickly, NOT so that you can reach 70 mph rapidly but so that you could over take quickly in an emergency.


We call the rate at which something can change its velocity the ACCELERATION of the object.

If the acceleration is positive the object is speeding up, if it is negative it is slowing down. We call this negative acceleration a DECELERATION or a RETARDATION.




Acceleration means an increase in velocity per second and so the units for acceleration are:

(metres per second) per second    written m/s².

Our bodies experience a whole range of accelerations during our lives.
A family car may reach 3 m/s² during acceleration, the acceleration of objects falling freely in the Earth's gravitational field is about 10 m/s² and pilots of military jets may reach up to 50 m/s².

However some animals can experience large accelerations, a perch may reach 33 m/s², a bush baby 180 m/s², a woodpecker 1000 m/s² when pecking and when a flea jumps it may achieve 1400 m/s²! The acceleration of a rifle bullet in the barrel of the rifle will be at least 200 000 m/s²!



Speed conversions
13.6 m/s (30mph) 22.7 m/s (50mph)
31.8 m/s (70mph) 45.5 m/s (100)mph