Question

a student wants to determine the effect of mass on kinetic energy. she will drop two balls of the same size into a pool of water. which investigation method should the student use? (1 point)
she should drop two balls with different masses from the same height
she should drop two balls of the same mass from the same height.
she should drop two balls of the same mass from different heights.
she should drop two balls with different masses from different heights.

Explanation:

To determine the effect of mass on kinetic energy, the student should use the method of controlling variables. Kinetic energy formula is \(KE=\frac{1}{2}mv^{2}\). When dropping objects, the velocity \(v\) just before hitting the water is related to the height \(h\) by \(v = \sqrt{2gh}\) (from \(v^{2}-u^{2}=2as\), where \(u = 0\), \(a = g\) and \(s=h\)). If we want to study the effect of \(m\) (mass) on \(KE\), we need to keep \(v\) (and thus \(h\)) constant. So we should vary the mass (\(m\)) while keeping the height (\(h\)) the same.

Answer:

She should drop two balls with different masses from the same height.