# Acceleration due to freefall

```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.
a) Find the greatest height reached by the ball.
b) Calculate the length of time the ball is more than 2.8m
above the ground.
the problem.
```

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