Forces on a particle and connected bodies – equilibrium, inclines, Atwood

What it shows

This lab covers forces on a particle in three settings. On a force table you add up to four forces, see their components, the resultant and the equilibrant, and check Lami's theorem for three forces. Gravesand's apparatus lets you measure angles and find an unknown weight with the parallelogram law. The inclined plane resolves the weight into W sin θ and W cos θ and shows limiting friction F = μN. The connected-bodies screen gives the acceleration and tension of an Atwood machine or a block pulled by a hanging mass. Strings are light, pulleys smooth, and kinetic friction equals μN.

How to use

Pick Equilibrium, Inclined plane or Connected bodies. On the force table choose a force under Edit force, then set Size and Direction or drag the arrow tip. Press Release to let the body move. Use Record to add a measurement to the table, and Cut string to cut the string while the bodies move. Enter your result in the task box and press Check.

Parameters you can change

• Screen Equilibrium, Inclined plane, Connected bodies
• Set-up on the Equilibrium screen Force table, Gravesand's apparatus
• Number of forces on the particle 2–4
• Size of F₁ 0–10 N
• Direction of F₁ from the x-axis 0–360 °
• Size of F₂ 0–10 N
• Direction of F₂ from the x-axis 0–360 °
• Size of F₃ 0–10 N
• Direction of F₃ from the x-axis 0–360 °
• Size of F₄ 0–10 N
• Direction of F₄ from the x-axis 0–360 °
• Mass of the particle 0.1–5 kg
• Body to weigh (Gravesand's apparatus) Test body 500 g, Body A, Body B, Body C
• Hanging mass on the left m₁ 50–1000 g
• Hanging mass on the right m₂ 50–1000 g
• Body on the inclined plane Roller 1.00 kg, Roller X (unknown mass), Wooden block on a rough plane
• Angle of the plane θ 0–60 °
• Mass of the wooden block 0.2–5 kg
• Coefficient of friction μ of the block 0–1
• Hanging mass M 0–8000 g
• Connected bodies Atwood machine, Block on a table and hanging mass, Block on an incline and hanging mass
• Mass m₁ 0.1–5 kg
• Mass m₂ 0.1–5 kg
• Coefficient of friction μ (connected bodies) 0–1
• Angle of the incline θ (connected bodies) 0–60 °

Questions to explore

1. What is special about the triangle of forces when three forces keep a particle in equilibrium?
2. Why is the graph of the balancing force against sin θ a straight line through the origin?
3. How does each body's acceleration change when the string is cut during the motion?