The rate of change of velocity
Rock is completely immersed in hot water. By the second law of thermodynamics, thermal energy or heat is transferred from substance with higher temperature to substance with lower temperature until they come to thermal equilibrium i.e. both at same temperature.
It is given here that rock is at 20°C which is at lower temperature than water at 80°C. ∴Heat or thermal energy flows from water to rock. So, right choice is-
A. The water gives the rock thermal energy and gets no thermal energy in return.
Answer: C. Radio-controlled toy airplane
Explanation:
Just did the quiz
a.
The work done by a constant force along a rectilinear motion when the force and the displacement vector are not colinear is given by:

where F is the magnitude of the force, theta is the angle between them and d is the distance.
The problen gives the following data:
The magnitude of the force 750 N.
The angle between the force and the displacement which is 25°
The distance, 26 m.
Plugging this in the formula we have:

Therefore the work done is 17673 J.
b)
The power is given by:

the problem states that the time it takes is 6 s. Then:

Therefore the power is 2945.5 W