THE PRACTICE STUDIO
Go slowly. Ask why. Make it yours.
PRACTICE / Connected bodies
Two hanging masses share an acceleration
Masses 3 kg and 2 kg hang from opposite ends of a string over an ideal pulley. They are released.
Find the acceleration magnitude.
Organize the givens & assumptions
- m₁ = 3 kg
- m₂ = 2 kg
g = 10 m/s²; massless inextensible string, frictionless massless pulley and no air resistance.
Study with a tutor prompt
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Problem: Two hanging masses share an acceleration
Masses 3 kg and 2 kg hang from opposite ends of a string over an ideal pulley. They are released.
Question: Find the acceleration magnitude.
Givens:
- m₁ = 3 kg
- m₂ = 2 kg
Assumptions: g = 10 m/s²; massless inextensible string, frictionless massless pulley and no air resistance.
Choices (LaTeX):
A. 0\ \mathrm{m\,s^{-2}}
B. 2\ \mathrm{m\,s^{-2}}
C. 10\ \mathrm{m\,s^{-2}}
D. 5\ \mathrm{m\,s^{-2}}
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.
Treat the pair as one system: the weight difference drives the total mass.
Choose a physical relation
The heavier mass descends while the lighter rises with the same acceleration magnitude; tension cancels when the equations are added.
Isolate what is asked
Treat the pair as one system: the weight difference drives the total mass.
Why is this step valid?
The driving weight difference accelerates both masses, so divide by their total mass.
Substitute and interpret
The acceleration is 2 m/s², below g because the rising mass opposes the descent.
Both individual force equations give the same string tension, confirming the common acceleration.
TRY THE IDEA AGAIN
Double both masses while preserving their ratio. What happens to acceleration?
YOUR LEARNING NOTE
How does this idea feel now?
Confidence is a reflection, not proof of mastery.
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