Two Multiple Choice Questions On Work And Energy?
1. King Kong falls from the top of the Empire State Building, through the air (aire friction is present), to the ground below. How does his kinetic energy (K) just before striking the ground compare to his potential energy (U) at the top of the building?
a.) K is equal to U
b.) K is greater than U
c.) K is less than U
d.) It is impossible to tell
2. Consides two mass m1 and m2 at the top of two frictionless inclined planes. Both masses start from rest at the same height. However, the plane of which m1 sits is at an angle of 30 degrees with the horizontal, while the plane of which m2 sits is at 60 degrees. If the masses are released, which is going faster at the bottom of its plane?
a.) m1
b.) m2
c.) they both are going the same speed
d.) cannot be determined without knowing the masses
Any help is appreciated.
1) K is less than U. some of the potential energy is lost to air friction.
2) C. Since the masses are on frictionless planes you can assume all the potential energy is converted to kinetic. M doesn’t matter because for either equation when you set KE equal to PE the M is on both sides and cancels. The only difference is the gentler slope cause slower acceleration for a longer time to reach the same final speed