A 20.0 kg rock is sliding on a rough , horizontal surface at8.00 m/s and eventually stops due to friction .The coefficient ofkinetic fricction between the rock and the surface is 0.20
what average thermal power is produced as the rock stops?

Therefore the average thermal power is = 19.61 W

Explanation:

Given that the mass of the rock = 20.0 kg

initial velocity (u) = 8.00m/s

Final velocity = 0

Kinetic fiction = 0.20.

Friction force = Kinetic fiction× weight

                      =

Force = mass × acceleration

To find the time , we use the the following formula,

v=u+at

Here a

⇒t = 4.08 s

Now,

Thermal energy= work done by friction = change of kinetic energy

The change of kinetic energy

=

=80 J

Thermal energy=80 J

Thermal power = Thermal energy per unit time

                          w

                         =19.61 W

Therefore 19.61 W average thermal power is produced as the rock stops.

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg