Question

A body is thrown vertically upwards with an initial velocity of 9.8 ms⁻¹. What is its speed and direction after (i) 1s (ii) 2s (g = 9.8 ms⁻²)?
Also, find the height to which it will rise.

Answer 1

(1) 0 meter/second(2) 9.8meter/second

Answer 2

Maximum height to which the stone can reach is 4.9 m.

Explanation:

As the stone is thrown upward the acceleration due to gravity is to be taken negative.

g = - 9.8 m/s2

Given that initial velocity u = 9.8 m/s

At the highest point, final velocity will be zero. v = 0

v2 - u2 = 2as

Substituting, we get:

0 - (9.8)2 = 2× (-9.8) × h  

- 9.8 / 2 = h  

h = 4.9 m  

So, the maximum height to which the stone can reach is 4.9 m.

Time take for the object to fall to ground will be:

s = ut + 1/2at^2

u will be 0 and s is 4.9m with g being positive.

4.9 = 0 + 1/2*9.8*t^2

t = 1 seconds