1. A Physics 7A student stands on a ladder and throws a 150g stone straight up in the air. As she lets go of the stone her
hand is 5m above the ground. The stone lands on a vertical spring attached to the ground, compressing it fully (10cm)
and the stone comes to rest at ground level. The spring constant is 104 N/m = 104 J/m2. What was the original speed
of the stone? You must apply the Energy Interaction Model to receive credit.
2. For two masses attached to an ordinary spring, with spring constant k and equilibrium separation r0, sketch PE versus
separation. Next, explain how you would go about plotting Etotal and KE for this system, given that the KE at r=1.5r0
is 10J. Finally, sketch these on your plot.
3. Your DL instructor throws a solid heat-pack (mass = 100g) straight up in the air and asks you to graph the PE, KE,
and Etotal between the time it leaves his hand and when it reaches the top of its flight path, motionless, 5m above the
point of release. Draw this graph accurately for this range of motion, setting y=0 at the top of the heat-pack’s flight
path.
4. Plot PEgrav versus height between y=0m and y=20m for a 0.5kg ball thrown straight up on Earth and, on the same
graph, for a ball thrown straight up on Jupiter (gJupiter = 2.5*gE). For each planet calculate the gravitational force at
two different heights and add arrows of appropriate proportional strength and direction to your plot.
Practice problems #1.
All problems copyright Maxwell Chertok, 2008. All rights reserved.