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1)Two different objects are dropped from rest off of a 50-m-tall cliff. One lands going 30% faster than the other. The two ojects have the same mass. How much more kinetic energy does one object have at the landing than the other? The answer is

**69% more**why???

2) A projectile is fired vertically at a speed of 30 m/s. It reaches a maximum height of 44.1 m. What fraction of its initial energy has been lost to air resistance at this point? the answer is

**2%**, can somebody explain me why?

3) At what height above the earth's surface is the acceleration due to gravity 10% of that at sea level? 1.36 x 10^7 m

4) The moon has 1/2 the acceleration of gravity of the earth. What would the mass of the earth have to be to have this acceleration at its surface? 1.03x10^3

I wouuld really appreciate if someone can help me, physics is my weakness :(