physics
posted by amanda .
Take the mass of the Earth to be 5.98 ×
1024 kg.
If the Earth’s gravitational force causes a
falling 74 kg student to accelerate downward
at 9.8 m/s2, determine the upward acceleration of the Earth during the student’s fall.
Answer in units of m/s2

Since the forces on student (due to Earth) and Earth (due to student)are equal and opposite,
F = m g = M a
a = (m/M)* = 1.24*10^23 g
= ?? 
Two marbles, one twice as massive as the
other, are dropped from the same height.
When they strike the ground, how does the
kinetic energy of the more massive marble
compare to that of the other marble?
1. It has twice the KE.
2. It has 4 times the KE.
3. It has onehalf the KE.
4. It has the same KE