For the gravitational force the formula is P.E. = mgh, where m is the mass in kilograms, g is the acceleration due to gravity (9.8 m / s2 at the surface of the earth) and h is the height in meters. Notice that gravitational potential energy has the same units as kinetic energy, kg m2 / s2.
No, only average speed can be calculated from the distance of 90 meters and the time 3 seconds hope this helps
The displacement of an object in relation to time is velocity.
Speed is similar, but it is actually the distance traveled in relation to time. The difference is that say if an object is spinning at one revolution per second, the speed of the edge is 'x' mps. The velocity on the other hand is 0 mps because the disk rotates at 1 rotation per second the displacement after one second is 0.