Answer:
(a) -472.305 J
(b) 1 m
Explanation:
(a)
Change in mechanical energy equals change in kinetic energy
Kinetic energy is given by
Initial kinetic energy is 
Since he finally comes to rest, final kinetic energy is zero because the final velocity is zero
Change in kinetic energy is given by final kinetic energy- initial kinetic energy hence
0-472.305 J=-472.305 J
(b)
From fundamental kinematic equation

Where v and u are final and initial velocities respectively, a is acceleration, s is distance
Making s the subject we obtain
but a=\mu g hence

Answer:
Water.
Explanation:
This means:
1) For the temperature of water to raise at any point to the next degree by 1°C, will require a specific heat capacity of 4.184 J/Kg°C
2) For the temperature of wood to raise at any point to the next degree by 1°C, will require a specific heat capacity of 1.760 J/Kg°C
Note that: specific heat is directly proportional to energy, therefore the higher the heat capacity, the higher the energy.
4.184 J/Kg°C is higher than 1.760 J/Kg°C, hence WATER needs more energy.