Question

A body of mass 2 kg is thrown vertically upwards with an initial velocity of 20m/s. What will be its kinetic ergy at the end of 2s ? ( Assume g = 10 m/s^2).

Answer 1

From equation of motion v=u-at

at 2 sec v= 20-2*10 = 0 m/s

⇒ The body has zero Kintic energy  and maximum potential energy.

Potential energy = 1/2 * 2 * 20² = 400 J

Answer 2

$Here \: is \: the \: answer \: of \: your \: question$

According to question we have given,

Mass (m) = 2 kg

acceleration due to gravity (g) = - 10 m/s²

[Because body is thrown vertically upward due to this g is - ve and g = a]

initial velocity (u) = 20 m/s

time (t) = 2 sec

Now,

Formula applied here is;

s = ut + ½ at²

s = 20 × 2 + ½ × (-10) × (2)²

s = 40 - ½ (10) × 4

s = 40 - 5 × 4

s = 40 - 20

s = 20 m

Now, we have to find it's kinetic energy at the end of the ground.

But during reaching the ground it's kinetic energy convert into potential energy.

So, that means we have to find it's potential energy.

[acceleration of gravity towards earth/ground always + ve]

So, g = + 10

Potential energy = mgh

Potential energy = 2 × 10 × 20

`$\textbf{Potential energy = 400 J}$`