Mechanics & Simple Machines · AP Physics 1 Unit 2 (Dynamics)
Newton's Second Law & Connected Bodies Simulator
Key exam takeaway: Overweight and weightlessness depend solely on the direction of acceleration, not the direction of velocity.
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3D Simulation Stage● 60 FPS
Parameter Controls
N
kg
kg
Live Derivations & Metrics
Acceleration a
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Tension / Normal Force
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Net Force
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Apparent Ratio (N/mg)
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Real-Time Formula Derivation
Governing Formula:
--Substitution:
--Regime: --
Worked Examples & Exam Question Deep Dive
Worked Problem
Problem: A 60kg person in an elevator accelerates up at 2m/s². What is the scale reading? What if accelerating down at 2m/s²?
Step-by-Step Derivation:
- Upward accel: N = m(g+a) = 60*(10+2) = 720N (overweight). Downward accel: N = m(g-a) = 60*(10-2) = 480N (underweight).
Worked Problem
Problem: Two blocks m1=3kg and m2=2kg connected by a string on floor with μ=0.1. A 20N pull acts on m1. Find a and string tension T.
Step-by-Step Derivation:
- Total friction f = 0.1*5*10 = 5N. Accel a = (20 - 5)/5 = 3m/s². Isolate m2: T - f2 = m2*a => T = 2*3 + 2 = 8N.
Student Inquiry Worksheet & Practice Problems
Q1. Variant 1: A 4kg object on frictionless surface is acted by 10N right and 6N left. Find acceleration.
Answer Key: Net force F = 10 - 6 = 4N right. Acceleration a = 4N / 4kg = 1 m/s² to the right.
Q2. Variant 2: A spring scale holding a 2kg mass reads 24N. Describe the possible motion states. (g=10m/s²)
Answer Key: Weight is 20N. Scale reads 24N > 20N, so a = (24-20)/2 = 2 m/s² upward. The object is either accelerating upward or decelerating downward.
Q3. Variant 3: A 1500kg car moving at 20m/s brakes under constant 6000N resistance. Find stopping time and distance.
Answer Key: Deceleration a = 6000/1500 = 4 m/s². Time t = 20/4 = 5s. Distance s = 20² / (2*4) = 50m.
Frequently Asked Questions & Misconceptions
Does overweight mean actual gravity increased?
No! Gravitational force G=mg remains constant. Overweight means normal force exceeds gravity due to upward acceleration.
How do strings and springs differ when cut?
Strings lose tension instantaneously. Springs maintain their deformation and tension at the exact moment of cut.
Does acceleration vanish immediately if force is removed?
Yes. By Newton's second law instantaneous principle, acceleration adjusts immediately with net force.
In a free-falling elevator, does a released apple hit the floor?
No. Both the person, apple, and elevator accelerate downward at g, so the apple hovers relative to the elevator cabin.