- A ball of mass 2 kg is gently pushed off the edge of a tabletop
that is 1.8 m above the floor. Find the speed of the ball as it strikes
the floor.
Here’s How to Crack It
Ignoring the friction due to the air, we can apply conservation of mechanical energy.
Calling the floor our h = 0 reference level, we write
Notice that the ball’s potential energy decreased, while its kinetic energy increased.
This is the basic idea behind conservation of mechanical energy: One form of
energy decreases while the other increases. (Also, notice that although the question
gives you the mass of the ball, it wasn’t necessary since the mass m cancelled out
of the equation.)
- A box is projected up a long ramp (incline angle with the
horizontal = 30°) with an initial speed of 8 m/s. If the surface of the