Work, Power and EnergyMedium
Question
A spherical ball of mass 2 kg falls from a height of 10 m and is brought to rest after penetrating 10 cm into sand. The average force exerted by sand on the ball is $\_\_\_\_$ N.
Options
A.1980
B.2020
C.2000
D.1000
Solution
Sol. [Key Concept: Work–energy over the total drop: $mg(h + d) = F\ d$.]
$$(\text{~}\text{W.D.}\text{~})_{g} + (\text{~}\text{W.D.}\text{~})_{\text{sand}\text{~}} = \Delta K$$
$$\begin{matrix} & 2 \times 10 \times \left( 10 + \frac{10}{100} \right) - F_{\text{sand}\text{~}} \times \left( \frac{10}{100} \right) = 0 = 0 \\ & {\text{ }F}_{\text{sand}\text{~}} = 2(10 + 0.1) \times 100 = 2020 \end{matrix}$$
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