Question

Exam 3 Name Problem(30 %), write your answer in the space provided or on a separate sheet of paper. You must show all work, starting with the equations provided on the exam, to recieve credit. 18) A man on a small boat (mass of man and boat together is 120 kg) throws a 5 kg suitcase to his wife on the dock 0 pts) assuming there is no friction between the boat and the water, with what velocity do the boat move after he throws the suitcase? b) (5 pts) does your answer pass the common sense test? Give man and specific reasons why or why not. c) (10) How much kinetic energy is added to the system by the throw? d) (5 pts) Where did the energy come from? What form was it in before?

Answer 1

a) This is found by the law of conservation of linear momentum.

If the velocity with which the suitcase is thrown by v then

51,-( 120-5)u'

$v' =\frac{v}{23}$

The boat recoils back with a velocity of v/23

b) This does pass the common sense test. Basically works on the principle of recoil. Just like the gun faces when fired. Also when we are advised to not something off the bus rather just place it slowly.

c)Kinetic energy added

= 0.5*5*v² + 0.5*115*(v/23)^2

=

60ひ2 3

d)This energy comes from the muscular energy with which the suitcase is thrown. It is stored in the body cells in the form of ATP