• Speed is the distance an object moves in a time frame. It is measured in metres/second (m/s) or kilometres/hour
(km/h).
speed = distance moved / time taken
• Calculating distance travelled: -with constant speed: speed × time -with constant acceleration: (final speed + initial speed)/2 × period of acceleration • Acceleration is the change in velocity per unit of time, measured in metres per second per second, or m/s2 or ms -2 . average acceleration = change in velocity / time taken a = v - u / s An increase in speed is a positive acceleration, a decrease in speed is a negative acceleration / deceleration / retardation. • If acceleration is not constant, the speed/time graph will be curved. • The downwards acceleration of an object is caused by gravity. This happens most when an object is in free fall (falling with nothing holding it up). Objects are slowed down by air resistance. Once air resistance is equal to the force of gravity, the object has reached terminal velocity. This means that it will stay at a constant velocity. (This varies for every object). The value of g (gravity) on Earth is 9.81m/s2 . However 10m/s2 can be used for most calculations. Gravity can be measured by using: Gravity = 2 x height dropped / (time)2 g = 2h / t2 This only works when there is no air resistance, so a vacuum chamber is required.
• Calculating distance travelled: -with constant speed: speed × time -with constant acceleration: (final speed + initial speed)/2 × period of acceleration • Acceleration is the change in velocity per unit of time, measured in metres per second per second, or m/s2 or ms -2 . average acceleration = change in velocity / time taken a = v - u / s An increase in speed is a positive acceleration, a decrease in speed is a negative acceleration / deceleration / retardation. • If acceleration is not constant, the speed/time graph will be curved. • The downwards acceleration of an object is caused by gravity. This happens most when an object is in free fall (falling with nothing holding it up). Objects are slowed down by air resistance. Once air resistance is equal to the force of gravity, the object has reached terminal velocity. This means that it will stay at a constant velocity. (This varies for every object). The value of g (gravity) on Earth is 9.81m/s2 . However 10m/s2 can be used for most calculations. Gravity can be measured by using: Gravity = 2 x height dropped / (time)2 g = 2h / t2 This only works when there is no air resistance, so a vacuum chamber is required.
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