A 20kg rock is sliding on a rough, horizontal surface at 8 m/s and eventually stops due to friction. the coefficient of kinetic friction between the rock and the surface is 0.200. what average power is produced by friction as the rock stops?

156watts

Explanation:

M = 20

U = 0.200

Vo = 8.0

We are to get p

P = w/t

W = 1/2(vf²-Vo²)

The final velocity is 0

W =-1/2*20*8²

= -640J

Acceleration = -ug

= -0.200*9.8

= -1.96m/s^-2

We are to get t

t = 8/1.96

= 4.1s

P = w/t

= 640/4.1

= 156 watts

156watts is the average power that is produced by friction as the rock stops.

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.