Two objects interact with each other and with no other objects. Initially, object A has a

speed of $6$ m$/$s$,$ and object B has a speed of $5$ m$/$s$.$ In the course of their motion, they

return to their initial positions. Then A has a speed of $4$ m$/$s$,$ and B has a speed of $3$ m$/$s$.$

We can conclude that

a$.$ mechanical energy was decreased by nonconservative forces.

b$.$ mechanical energy was decreased by conservative forces.

c$.$ the potential energy changed from the beginning to the end of the trip.

d$.$ mechanical energy was increased by nonconservative forces.

e$.$ mechanical energy was increased by conservative forces.

$6.$ If the collision time between a baseball and a glove is doubled, the force required to catch

the ball is

a$.$ one$-$fourth of the original force.

b$.$ remains unchanged.

c$.$ is doubled of the original force.

d$.$ is quadrupled of the original force.

e$.$ is halved of the original force.

$7.$ A soccer player tosses a $0\mathrm{.}3$ kg ball vertically and then stands underneath it$.$ As it

descends, he bumps it vertically upward with his head. If it was descending at $2\mathrm{.}0$ m$/$s$,$

rebounds with a speed of $3\mathrm{.}0$ m$/$s$,$ and the soccer player exerts an upward force of $150$ N

on the ball, how long was the soccer player's head in contact with the ball?

$8.$ An empty coal car of a train of mass $8000$ kg is moving at $12$ m$/$s along rails. $24000$ kg of

coal is dumped into the car from a motionless bin. What is the speed of the coal car

afterward?

$9.$ Jupiter has a moon called Io$,$ which has an orbital period of $1\mathrm{.}77$ days and a semi$-$major

axis of $4\mathrm{.}22$ x $108$ m$.$ Based on this data, what is the mass of Jupiter?

$10.$ Chandra weighs $686$ N on Earth. How much will Chandra$$s weight be if he goes to

Jupiter? Jupiter is $319$ times heavier and $11$ times bigger than the Earth.