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Complete question:
A fireman of mass 80 kg slides down a pole. When he reaches the bottom, 4.2 m below his starting point, his speed is 2.2 m/s. By how much has thermal energy increased during his slide?
Answer:
The thermal energy increased by 3,099.2 J
Explanation:
Given;
mass of the fireman, m = 80 kg
initial position of the fireman, hi = 4.2 m
final speed, v = 2.2 m/s
The change in the thermal energy is calculated as;
ΔE + (K.Ef - K.Ei) + (Uf - Ui) = 0
where;
ΔE is the change in the thermal energy
K.Ef is the final kinetic energy
K.Ei is the initial kinetic energy
Uf is the final potential energy
Ui is the initial potential energy
Here we can use momentum conservation as there is no external force on sled and child while he jump on sled
by momentum conservation equation
since sled and child both moves with same speed so here they both will have same final speed "v"
by solving above equation we will have
25 v = 80
v = 3.2 m/s
So they will move together with speed 3.2 m/s
