Question

A girl swings on a playground swing in such a way that at her highest point she is 3.9 m from the ground, while at her lowest point she is 0.9 m from the ground. 9.9 m 3.9 m 0.9 m What is her maximum speed? The acceleration due to gravity is 9.8 m/s 2 .

Answer 1

Answer:

Explanation:

Given

height of girl at top point is $h_1=3.9\ m$

height at bottom point is $h_2=0.9\ m$

Suppose girl possess maximum velocity at bottom point so her kinetic energy is converted to Potential energy

kinetic energy $K=\frac{1}{2}mv^2$

Gain in Potential Energy $\Delta U=mg(h_1-h_2)$

$K=\Delta U$

$\frac{1}{2}mv^2=mg(h_1-h_2)$

$v=\sqrt{2g(h_1-h_2)}$

$v=\sqrt{2\times 9.8\times (3.9-0.9)}$

$v=\sqrt{58.8}$

$v=7.66\ m/s$