KE, GPE & EPE Flashcards

All 4 cards in this deck

What are the steps to find the speed of an object dropped from a height (no air resistance)?
e.g. dropped from 5 m, $g = 9.8$ N/kg

1. $mgh = \frac{1}{2}mv^2$, masses cancel so $v^2 = 2gh$
2. Substitute: $v^2 = 2 \times 9.8 \times 5 = 98$
3. $v = \sqrt{98} = 9.9$ m/s

What are the steps to find the energy dissipated when an object slides down a slope?
e.g. it loses 500 J from its gravitational potential store and has 400 J of kinetic energy at the bottom

1. Find the decrease in the GPE store: 500 J
2. Find the kinetic energy at the bottom: 400 J
3. Subtract: $500 - 400 = 100$ J dissipated

True or false? On a frictionless slide, riders of different mass reach the same speed at the bottom.

True. Masses cancel in $mgh = \frac{1}{2}mv^2$, so the final speed depends only on the vertical height (and $g$).

A baby bouncer: describe the energy stores as the baby moves down from rest to its lowest point.

The gravitational potential store decreases, transferring to the kinetic store and then to the elastic potential store of the spring; at the lowest point it is all elastic potential.