Question

A ball of mass 200 gm Falls from a height of 5 metres calculate its kinetic energy when it just reaches the ground? (g=10ms-2) ​

Answer 1

Total mechanical energy is conserved

this means all potential energy is converted to kinetic energy

Final Kinetic Energy = initial potential energy = 0.2 × 10 × 5 J = 10J

Answer 2

Question :-

A ball of mass 200 gram falls from a height of 5 meters calculate it's kinetic energy when it just reaches the ground ? (g = $10 \: m s^{-2}$ )

Answer :-

Given :-

• Mass of Ball = 200 grams or 0.2 kg

• Height = 5 m

• g = $10 \: m s^{-2}$

♦ Then to find out kinetic energy we must find out the velocity when just it touches the ground .

• From motion equation

$v^2 = u^2 + 2as$

• As initial velocity = 0

$\implies v^2 = 0^2 + 2 (-10)(-5)$

$\implies v^2 = 100$

$\implies v = \sqrt{100}$

$\implies v = 10 \: ms^{-1}$

♦ Now as we know that Kinetic Energy

= $\dfrac{1}{2} mv^2$

• Then by putting values

= $\dfrac{1}{2} 0.2 \times (10)^2$

= $\dfrac{1}{2} 0.2 \times 100$

= $\dfrac{20}{2}$

= 10 Joules