What is the reason that a fixed pulley makes work easier

Erosion of the beach is normally a slow process. however, in certain situations, large chunks of shore may wash out to sea. what could cause this to happen?

Select all of the following that are equal to an impulse of 20 unitsa) force= 5, time= 5.5b) force= 25, time= 0.8c) force= 0.1, time= 200d) force= 10, time= 2(its b, c, and d)(also in order to find answer they have to add to get the unit)ex= 25x.8=20 or .1x200=20

Agirl throws a ball. if the ball's acceleration is 12 m/sec/sec and its mass is 0.5 kg, how much force did the girl apply to the ball?