# Gravitation: Potential

### Problems for Principle of Equivalence and Tides

Problem : A rocket taking off from the earth is accelerating straight upwards at 6.6 m/sec 2 . How long will it take an apple of 0.2 kilograms to hit the floor of the rocket if it is dropped from a height of 1.5 meters?

Problem : If you measure the speed of light on earth, will the result be the same as of you measured it in interstellar space, far from any gravitational fields?

Problem : If wood was found to fall at a different rate to plastic (ie. g wood g plastic ), what would be the consequences for the principle of equivalence?

Problem : A mass M is at the origin. Two masses m are at points (R, 0) and (R + x, 0) where x < < R . What is the difference in the gravitational force on the two masses? This is the longitudinal tidal force. (Hint: make some approximations)

Problem : Again, a mass M is at the origin. Now, two masses are at (R, 0) and (R, y) , where y < < R . What is the difference in the gravitational force on the two masses, and what is its effect? This is the transverse tidal force.

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