A 152 kg boat is at rest in a calm lake at the end of a dock. A 85.6 kg person running down the dock leaps into the boat with a horizontal velocity of 4.58 m/s. Ignore all effects of friction and resistance due to the water.
a) Find the kinetic energy of the person before jumping into the boat.
b) If the person lands in the boat and they move off together, find the velocity of the combined object just after the collision.
c) Find the total kinetic energy just after the collision.
d) Is the collision elastic or inelastic? Use your answers to parts a & c to justify your answer.
Here are answers but i can't figure out how to get these
a) 898 J b) 1.65 m/s c) 323 J d) inelastic, since KEo KE
(a) KE₁ =m₁v²/2 =85.6•4.58²/2=897.8 =898 J.
I also can’t obtain the suggested answer (b) and, as a result, the answer (c)
(b) According to the law of conservation
of linear momentum
m₁v =(m₁+m₂)u
u= m₁v/(m₁+m₂)=85.6•4.86/(85.6+152) = 1.75 m/s
(c) KE =(m₁+m₂)u²/2= (85.6+152) •1.75²/2=363 J
(d) inelastic, since KE₁ ≠ KE