Question

question 4 of 10
a ball of mass 0.2 kg is dropped from a height of 10 m. how much mechanical energy does it have right before it hits the ground? (assume there is no air resistance.) acceleration due to gravity is ( g = 9.8 , \text{m/s}^2 ).

a. 19.6 j
b. 25.4 j
c. 0 j
d. 10.0 j

Explanation:

Step1: Determine the mechanical energy conservation

In the absence of air resistance, mechanical energy \(E\) is conserved. So the mechanical energy just before hitting the ground is equal to the initial mechanical energy.

Step2: Calculate the initial mechanical energy

The ball is dropped (initial velocity \(v = 0\)), so initial mechanical energy \(E\) is just potential energy \(E = mgh\). Given \(m=0.2\space kg\), \(h = 10\space m\), \(g=9.8\space m/s^{2}\). Then \(E=(0.2\space kg)\times(9.8\space m/s^{2})\times(10\space m)=19.6\space J\)

Answer:

A. 19.6 J