Answer to Question #251649 in Physics for Cha

Question

A ball is at rest from the field and some people are running towards it and the ball has a mass of 12 kgs and is in a lift with 3m above the ground , what could possibly the energy o f it if it rolls 8m/s and the second person speeds tha ball by 80 percent and the third person decelerates the ball by 80 percent ending the ball travel at 1500 meters across the field

Answer 1

The energy of the ball when it is 3 m above the ground and moving at 8 m/s is

$$E=\frac12 mv^2+mgh=737\text{ J}.$$

The energy when it rolls on the ground at 1.8 of the 8 m/s:

$$E_1=\frac12m(1.8v)^2=1244\text{ J}.$$

When the second person decreases the speed by 80% and the ball rolls on the ground:

$$E_1=\frac12mv^2=384\text{ J}.$$