Calculate the force of gravity of a 25kg block resting on the earth (M=5.97x10^24kg). The radius of the earth is 6.38x10^6m. I already know...

But I don't understand what steps I have to take to solve that equation

Steelhead trout migrate up stream to spawn.occasionally they need to leap up small waterfalls to continue their journey. fortunately, steelhead are remarkable jumpers, capable of leaving the water at a speed of 8.0 m/s. a. what is the maximum height a steelhead trout can jump? b.leaving the water at 8.0 m/s, the trout lands on top of the water fall 1.8 m high. how long was it in the air?