Topic · 3 games

Statics: when the forces cancel

An object stays at rest when the forces on it cancel, ΣF = 0, and the turning effects cancel too, ΣM = 0. Those two conditions size every cable, place every child on a seesaw, and decide how much each support of a bridge must carry.

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3 games

PLAY NOW · 32

Hanging Sign: Balance the Cables

Hang a 20 kg sign from one or two cables. Use ΣF = 0 to find each tension, discover why flat cables pull much harder, and find the shallowest angle a cable can take.

Force equilibriumTension
Play Hanging Sign
Up and down
Σ T·sin θ = W
Across
T₁·cos θ₁ = T₂·cos θ₂

PLAY NOW · 33

Seesaw: Balance the Torques

Balance a seesaw with children of different masses. Use torque, weight × distance, to place them, include the plank's own weight, and find the force that lifts a wheelbarrow.

TorqueRotational equilibrium
Play Seesaw
Balance
ΣM = 0
Torque
M = m·g·d

PLAY NOW · 34

Plank Bridge: Share the Load

Load a plank resting on two supports. Use ΣF = 0 and ΣM = 0 to find each support's reaction, include the plank's weight, and find where a support cracks or the plank tips.

Static equilibriumSupport reactions
Play Plank Bridge
Forces
R_A + R_B = W + w
Moments about A
R_B·L = W·x + w·x_c

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