What is the energy of a 15kg book sitting on top of a 2.5m bookshelf

We put a force of 50n on an object and the acceleration is 100 m/s². what is the mass of the object?

Atruck travels at an average speed of 70 km/hr. if it travels 100 km in the first hour, how far will it go the second hour of a 2 hour trip? if you could also give me the steps that would great.

Ahockey puck sliding along frictionless ice with speed v to the right collides with a horizontal spring and compresses it by 3.0 cm before coming to a momentary stop.