law+of+conservation+of+energy


 * The law of of energy :**

1. Consider the falling and rolling motion of the ball in the following two resistance-free situations. In one situation, the ball falls off the top of the platform to the floor. In the other situation, the ball rolls from the top of the platform along the staircase-like pathway to the floor. For each situation, indicate what types of forces are doing work upon the ball. Indicate whether the energy of the ball is conserved and explain why. Finally, fill in the blanks for the 2-kg ball.

The only force doing work is gravity. Since it is an internal or conservative force, the total mechanical energy is conserved. Thus, the 100 J of original mechanical energy is present at each position. So the KE for A is ** 50 J **. The PE at the same stairstep is ** 50 J (C) ** and thus the KE is also ** 50 J (D) **.

Using the equation ** KE = 0.5*m*v2 **, the velocity can be determined to be ** 7.07 m/s for B and E ** and ** 10 m/s for H and K **. The answers given here for the speed values are presuming that all the kinetic energy of the ball is in the form of translational kinetic energy. In actuality, some of the kinetic energy would be in the form of rotational kinetic energy. Thus, the actual speed values would be slightly less than those indicated. (Rotational kinetic energy is not discussed here at The Physics Classroom Tutorial.)



1. As the object moves from point A to point D across the surface, the sum of its gravitational potential and kinetic energies remains the same.

2. The object will have a minimum gravitational potential energy at point b.