Question

A ball of mass 200g falls from a height of 5 meters . what is it's kinetic energy when it just reaches the ground?​

Answer 1

Explanation:

To Find :

• kinetic energy of ball

Solution :

• mass of ball = 200g = 0.2 kg
• Height = 5m
• Acceleration due to gravity (g) = 9.8m/s²
• Initial velocity (u) = 0
• Final velocity (v) = ?

• By using Third Equation of Motion

• $\underline{\boxed{\blue{\star{\textrm{V² = u² + 2gh}}}}}$

v² = 0 + 2 × 9.8 × 5

v² = 98

v = √98

v = 7√2

• $\underline{\boxed{\blue{\star \: \: {\bf{k_e = \frac{1}{2} m {v}^{2} }}}}}$

k = 1/2 × 0.2 × (7√2)²

k = 0.1 × 98

k = 9.8 J

$\large\dag \large { \red{\underline{\bf{Hence }}}}$

$\pink{\textrm{Kinetic energy of ball is 9.8 Joules}}$

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${\underline{\green{\large{\textrm{More Information:-}}}}}$

Kinetic Energy : -

The energy of a body due to it's motion is called kinetic energy.

Formula :

• ${\red{\star \: \: {\bf{k_e = \frac{1}{2} m {v}^{2} }}}}$

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Answer 2

height=5m.

mass=200g (0.2 kg)

g=9.8m/s^2

∴ potential energy=mgh

                        = 0.2*5*9.8

                        = 9.8 J

∵ P.E at the highest point= K.E at the lowest point (when it is just about to hit the ground)

∴ K.E energy will be= 9.8 J