Equilibrium - Forces | Show Me The Physics

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Equilibrium — the state in which the resultant (net) force acting on an object equals zero

What is the resultant of these 2 forces?

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G. Equilibrium

resultant = 0 N

Ex 1

Given

What is the resultant of these 2 forces?

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At Equilibrium:

F_net = 0, a = 0

Velocity is Constant (rest or constant v)

Ex 2

Given

Could the forces of 8 N, 6 N and 4 N ever produce a state of equilibrium?

If so, find the resultant of the forces 4 N and 6 N.

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Answer: Yes

Resultant of 4 N and 6 N = 8 N

Ex 3

Given

Could the angles of these forces ever be arranged to produce equilibrium?

4 N and 5 N force diagram at various angles

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Answer: NO

4 N and 5 N have a range of possible resultants: 1 N to 9 N

Ex 4

Given

Could these forces ever be in equilibrium?

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Answer: No

50 N and 15 N have a range of 65 N to 35 N

Carl and Johnny playing king of the mountain

Which Diagram Shows Equilibrium?

Given

Which diagram represents a box in equilibrium?

Diagram 1

Diagram 2

June 2008 #9

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Answer

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Check Your Understanding

5 quick questions — pick an answer to see if you’re right.

1. When is an object in equilibrium?

2. A hockey puck slides across frictionless ice at a constant 5 m/s. Is it in equilibrium?

3. Which pair of forces, acting alone on an object, could produce equilibrium?

4. Forces of 8 N, 6 N and 4 N act on an object. Could they produce equilibrium?

5. Forces of 4 N and 5 N act on an object. What third force could put it in equilibrium?

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