Chapter 2 - Kinematics: Description of Motion - Learning Path Questions and Exercises - Exercises - Page 64: 69

$a).$ (1) less than 95%, $b).$ Height = 3.6m.

S=4.0m $v^{2}=u^{2}+2aS=0+(2\times 9.8\times 4)=78.4$ $v=8.85m/s$ 95% of impact velocity = ($0.95\times 8.85) =8.4m/s$ Using the same equation of motion, $0=8.4^{2}-2\times 9.8\times S$ or, $S=3.6m$ This as a percentage of original height $=\frac{3.6}{4}\times 100=90%$ which is less than 95%. a). (1) less than 95%, b). Height = 3.6m.