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71) A .2kg ball is dropped from 10 m above the beach, leaving an impression in the sand 5.0 cm deep. What is the average force acting on the ball by the sand?

So far I have converted 5.0cm to .05m. I calculated Fg= .2 kg (9.8m/s2) = 1.96 N. Now I am confused as to how I should calculate the normal force of the sand.

73) On an inclined plane (with angle of 37 degrees) a pulley is holding block m1 on the incline and block two is hanging on the other side. The weights of the blocks are m1= 3.0kg, m2= 2.5kg. What is the tension in the string if the acceleration is 1.2 m/s2?

I calculated T= m2a = (2.5kg)(1.2m/s2) = 3 N but the answer in the back of the book says it should be 21 N?

Thanks again for the help- I really appreciate it!