Respuesta :
Answer:
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 [tex](\mu_k)[/tex] = 0.20.
Friction force = Kinetic fiction× weight
=[tex]\mu_k mg[/tex]
Force = mass × acceleration
[tex]\Rightarrow acceleration =\frac{Force}{mass}[/tex]
[tex]=-\frac{\mu_kmg}{m}[/tex]
[tex]=-\mu_kg[/tex]
To find the time , we use the the following formula,
v=u+at
Here a [tex]=-\mu_kg[/tex]
[tex]\Rightarrow 0=8+(-\mu_kg)t[/tex]
[tex]\Rightarrow 0.20 \times 9.8\times t=8[/tex]
⇒t = 4.08 s
Now,
Thermal energy= work done by friction = change of kinetic energy
The change of kinetic energy
= [tex]\frac{1}{2} mu^2-\frac{1}{2} mv^2[/tex]
[tex]=\frac{1}{2}\times 20\times 8 -\frac{1}{2}\times 20\times 0[/tex]
=80 J
Thermal energy=80 J
Thermal power = Thermal energy per unit time
[tex]=\frac{80}{4.08}[/tex] w
=19.61 W
Therefore 19.61 W average thermal power is produced as the rock stops.
