Every mass is attracted to every other mass with a force that is proportional
to the product of both masses and inversely proportional to the square of the
distance between their centers of mass. The forces act along the line between
their centers of mass.
(a). The power of the candy bar is,

The time taken to play on 800 kJ energy of the candy bar is,

where E is the energy.
Substituting the known values,

As 1 minute is equal to 60 seconds,
Thus,

Thus, the time taken to play tennis on the 800 kJ energy is 30.3 minutes.
(b). By doing the exercise, the process of digestion of food inside our body increases. Thus, the exercise does not helps us to burn the calories. But it helps us to diggest the heavy meal like candy bar easily.
The time taken to digest the canndy bar or to utilise its energy is large because it takes a lot of time to burn small amount of food and make it digest quickly.
By the work-energy theorem, the total work done on the mass by the spring is equal to the change in the mass's kinetic energy:
<em>W</em> = ∆<em>K</em>
and the work done by a spring with constant <em>k</em> as it gets compressed a distance <em>x</em> is -1/2 <em>kx</em> ²; the work it does is negative because the restoring force of the spring points opposite the direction in which it's getting compressed.
So we have
-1/2 <em>k</em> (0.15 m)² = 0 - 1/2 (2.0 kg) (3.0 m/s)²
Solve for <em>k</em> to get <em>k</em> = 800 N/m.
Answer:
Wc = 7.84 weight of crown
Ww = 7.84 - 6.86 = .98 weight of water displaced
Density = 7.84 / .98 = 8 crown is 8 X that of water
Since gold has a density of 19.3 that of water the crown is certainly not 100 percent (if any) gold
While the boy is sitting on the chair it creates a force downward on the chair and therefore the chair takes it and gives off the equal amount of force. So while he is putting force downward the chair is putting the same force upward.