P8: Forces in Balance

What is the difference between scalar and vector quantities?

• Scalar quantities have magnitude only, such as distance, speed, mass, energy, and temperature.

• Vector quantities have both magnitude and direction, such as displacement, velocity, acceleration, force, and momentum.

How are vector quantities represented visually?

Represented by an arrow where the length of the arrow shows the magnitude and the direction of the arrow shows the direction of the vector.

What is the difference between contact and non-contact forces?

• Contact forces act between objects that are physically touching, such as friction, air resistance, tension, and normal contact force.

• Non-contact forces act between objects that are physically separated, such as gravitational force, electrostatic force, and magnetic force.

What is the difference between mass and weight?

• Mass is the amount of matter in an object, measured in kilograms, and stays constant regardless of location.

• Weight is the force acting on an object due to gravity, measured in newtons, and depends on gravitational field strength.

What is center of mass?

The single point on an object through which its entire weight can be considered to act.

What is a resultant force?

A single overall force that has the same effect as all the individual forces acting on an object combined.

What happens when the resultant force acting on an object is zero?

• A stationary object remains stationary.

• A moving object continues moving at a constant speed in a straight line with constant velocity.

How do you resolve a single force into two components?

Split the single acting vector force into two perpendicular component forces acting at right angles, usually horizontally and vertically.

How do you determine the resultant of two forces acting at right angles?

Draw a vector triangle joining the forces tip-to-tail, then draw the resultant hypotenuse from start to finish and measure its magnitude and angle.

What is a moment and how is it defined?

The turning effect of a force around a pivot, calculated as the force multiplied by the perpendicular distance from the pivot to the line of action of the force.

What is the principle of moments for a balanced system?

For an object in rotational equilibrium, the total sum of clockwise moments about a pivot equals the total sum of anticlockwise moments about the same pivot.

How do levers act as force multipliers?

Use a small input force applied at a large distance from a pivot to create a larger output force at a shorter distance.

How do gears transmit rotational effects?

• Interlocking teeth transmit rotational forces from one gear to another.

• Connecting a small gear to a larger gear increases output turning force or moment while decreasing output rotational spee