The initial kinetic energy of the boat and its rider is

After Sam stops it, the final kinetic energy of the boat+rider is

because its final velocity is zero.
For the law of conservation of energy, the work done by Sam is the variation of kinetic energy of the system:

where the negative sign is due to the fact that the force Sam is applying goes against the direction of motion of the boat.
A. <span>Standing is health-enhancing because it uses energy.
Because standing can burn a lot of calories.</span>
Explanation:
Velocity = displacement / time
v = √((58 m)² + (135 m)²) / (12 min × 60 s/min)
v = 0.20 m/s
Hubble noticed that the galaxies were moving away from us, which meant the universe was expanding.
This is why constellations change over time. In some years, the Big Dipper won't actually look like a dipper anymore.