THE PRACTICE STUDIO
Go slowly. Ask why. Make it yours.
PRACTICE / Inelastic collisions
From a collision to a pendulum rise
A 0.010 kg projectile moving horizontally at 100 m/s embeds in a stationary 0.990 kg pendulum block. The combined mass then rises freely.
Find the maximum vertical rise after impact.
Organize the givens & assumptions
- m = 0.010 kg
- M = 0.990 kg
- u = 100 m/s
g = 10 m/s²; negligible horizontal external impulse during impact; projectile sticks; no dissipative loss during the subsequent swing.
Study with a tutor prompt
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Problem: From a collision to a pendulum rise A 0.010 kg projectile moving horizontally at 100 m/s embeds in a stationary 0.990 kg pendulum block. The combined mass then rises freely. Question: Find the maximum vertical rise after impact. Givens: - m = 0.010 kg - M = 0.990 kg - u = 100 m/s Assumptions: g = 10 m/s²; negligible horizontal external impulse during impact; projectile sticks; no dissipative loss during the subsequent swing. Choices (LaTeX): A. 0.10\ \mathrm m B. 500\ \mathrm m C. 0.050\ \mathrm m D. 5\ \mathrm m Ask for my approach first. Help me distinguish a physical misconception from an algebra error without revealing which choice is correct. Tutoring approach: Act as a patient physics tutor. Ask what I understand and what I have tried, then wait for my reply. Teach one step at a time; do not give the final answer or a complete solution immediately. Start with a physical picture. Define unfamiliar symbols and operators, explain signs and units, and state the model's assumptions. Give progressively stronger hints only when I need them. Ask me to predict a change before calculating it. When I finish, help me check dimensions and a limiting case, then ask one related transfer question. If information is missing or ambiguous, ask rather than inventing it. Distinguish exact results from approximations and acknowledge uncertainty.
Start with the smallest hint.
Work through it with me.
One decision at a time. Pause, predict, then unpack the algebra.
Use horizontal momentum during impact, then convert the combined mass’s remaining kinetic energy into height.
Choose a physical relation
Momentum is conserved during the brief sticking impact; mechanical energy is conserved only in the later rise.
Isolate what is asked
Use horizontal momentum during impact, then convert the combined mass’s remaining kinetic energy into height.
Why is this step valid?
First find the common impact speed, then use that speed in the gravitational energy balance.
Substitute and interpret
The combined mass starts its swing at 1 m/s and rises 0.050 m; impact has already removed kinetic energy.
The rise uses the post-collision 0.5 J, not the projectile’s original 50 J.
TRY THE IDEA AGAIN
Can the projectile's entire initial kinetic energy be set equal to the final gravitational gain?
YOUR LEARNING NOTE
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