1. A 2 kg ball moves at 5 m/s. Calculate its kinetic energy.
   

1. A 3 kg object is held 4 m above the ground. Calculate its gravitational potential energy.
   

1. An object has 35 J of kinetic energy and 65 J of potential energy. Calculate its total mechanical energy.
   

1. A 5 kg scooter moves at 2 m/s. Later, its speed doubles to 4 m/s. Calculate its kinetic energy at both speeds and explain the change.