Question

A body of mass 1kg is thrown vertically upward ☝ from the ground with the velocity which is just sufficient to reach the top of a tower of height 40m. Find the kinetic energy ⚡ and velocity of the body when it is half-way up. Take g= 18m/s2

Answer 1

We have given that,

m = 1 kg

g = 10 ms-2

h = 40 m

And we know that after reaching the height 40m the objects final velocity will be 0. Also it will receive a negative acceleration.

First of all we have to find its initial velocity. For this we will use (2as = v2- u2​)

= 2 * -10 * 40 = 0-u2

=-800 = -u2

Therefore, u = 28 ms-1

Now we have to find its velocity when it is half way, it will be 'v'

s = v2- u2​​/ 2a

= 20 = v2 - 784/20

= v2 = 400

v = 20

Now kinetic energy of the object = 1/2mv2

= 1/2 * 1 * 400

= 200 joules

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