Question

a ball is thrown initial velocity 15.4ms for how long is the ball higher than 10.5 metres?

dont know how to work it out.

Answer 1

Initial velocity of the ball .

I am assuming that the ball is throwing upwards so that the acceleration due to gravity is negative.

We have the relation of motion .

Here v is final velocity, u is initial velocity, a is acceleration due to gravity, s is displacement.

We know that acceleration due to gravity is .

Since the ball is moving upwards, final velocity is zero i.e .

On substituting

Since the acceleration is decreasing .

The ball can go upto 12.1m.

To find how long it is higher than 10.5m, subtract 10.5 from 12.1.

.

So, it is 1.6 meters higher.