1.a) If you lift a backpack up, does the force exerted by you on
the backpack do positive, negative, or zero work? Explain your
reasoning.
b) If you lower lower a backpack, does the force exerted by you
on the backpack do positive, negative, or zero work? Explain your
reasoning.
c) If you move a backpack horizontally with constant velocity,
does the force exerted by you on the backpack do positive,
negative, or zero work? Explain your reasoning.
2.
A...