Force, Friction, and Equilibrium

State the principle of moments

• A When a system is in equilibrium, the sum of the total clockwise moment is equal to the sum of the total anti-clockwise moment about the same pivot.

• B When a system is in equilibrium, the sum of the total clockwise moment is greater the sum of the total anti-clockwise moment about the same pivot.

• C When a system is in equilibrium, the sum of the total clockwise moment is less than the sum of the total anti-clockwise moment about the same pivot.

• D When a system is in equilibrium, the sum of the total clockwise moment is equal to the sum of the total anti-clockwise moment about the different pivot.

The figure below shows a man lifting a heavy rock using a steel bar. He pushes downwards on the end of the bar with a force F. Which pivot positions allows the force F to be as small as possible?

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Tags

NGSS.HS-PS2-1

What is the anticlockwise moment acting on this crane?

• 80,000Nm
• 100,000Nm
• 120,000Nm
• 140,000Nm

Two masses of mass 10.0 and 6.0 kg are hung from massless strings at the end of a light rod. The rod is virtually weightless. A pivot (fulcrum) is placed off center and the system is free to rotate. If the 6.0 kg mass is 4.0 m away from the pivot, how far away is the 10.0 kg mass if the system is not rotating?

• 0.42 m

• 2.4 m

• 4.8 m

• 4.2 m

Assuming the system is in equilibrium, calculate the missing distance d

• 3.4 m

• 2.8 m

• 4.4 m

• 1.6 m

A boy of weight 600N sits on the see-saw as shown at a distance of 1.5m from the pivot. What is the force F required at the other end to balance the see-saw?

• 450 N

• 350 N

• 4.5 N

• 200 N

What is the size of the moment shown by the black arrow?

• 30 Nm

• 36 Nm

• 40 Nm

• 60 Nm

What to we call forces applied to anything that turns?

• Minute

• Moment

• Minimum

• Monument

What sense does the vector have?

• down and right

• up and left

• up and right

• down and left

What is the resultant vector's force?

• 10

• 20

• -10

• 14.14

Tags

NGSS.HS-PS2-1