Acceleration due to freefall The uniform acceleration formulae can be used when dealing with ‘free’ fall under gravity. Under such circumstances the ‘acceleration due to gravity’ is approximately 9.8 m/s2. (This value is often taken to be 10 m/s2 for convenience)
Example A brick is thrown vertically downwards from the top of a building and has an initial velocity of 1.5m/s. If the height of the building is 20m, taking g = 10 m/s2 find a) The velocity with which the brick hits the ground, b) The time taken for the brick to fall.
Example A ball is thrown vertically upwards with a speed of 14.7 m/s from a platform 19.6m above level ground. Calculate, a) The time taken for the ball to reach the ground b) The speed of the ball when it reaches the ground.
Example A particle is projected vertically upwards with a speed of 34.3 m/s. Find how long after projection the particle is a) At its maximum height b) At a height of 49m above the point of projection for (i) the first time (ii) the second time.
Example A ball is thrown vertically upwards with a velocity of 34.3m/s. Find how long after projection the particle is at a height of 49m above the point of projection for a) The first time b) the second time.
1.A level past paper question • A ball is thrown vertically upwards from the ground with initial speed 11.2 m/s. • Find the greatest height reached by the ball. • Calculate the length of time the ball is more than 2.8m above the ground. • State one assumption you have made in your solution of the problem.