Physics - Mechanics

Forces, Motion, and objects in motion.

What is the difference between a scalar and vector?

Scalars - Magnitude
Vectors - Magnitude AND Direction

How do you add vectors when they are either Perpendicular or not?

If Perpendicular:
1 - Use Pythagoras (a² + b² = c²)
2 - Use Trigonometry to find Direction (Cos/Sin Rule)

If Otherwise:
Use Scale Diagram

• Make sure to use rule and protractor

• write down scale that you are using to represent the image accurately

How do you resolve vectors?

After drawing correct diagram,
if moving along angle from original vector, use COS θ x Force.

If moving away from angle, use Sin θ x Force

What does “In Equilibrium” mean?

Resultant Force is 0.

Therefore, object is either stationary or at constant speed.

How can one show object is in equilibrium?

1 - Sum of vertical and horizontal components of forces acting on object.

2 - Closed triangle diagram (3 forces)

Moment Formula.

Moment = Force x Perpendicular Distance from point to line of action of force.

What is a couple? and what is different for a couple?

A couple is a pair of coplanar forces that have equal magnitude but opposite directions.

To calculate its moment, it is:
Force x perpendicular distance between Lines of action of force.

State the Principle of moments.

Sum of Anticlockwise moments is equal to the sum of Clockwise moments.

What does “uniform” mean?

Centre of Mass is ALWAYS at the centre of the object.

What is Centre of Mass?

The point at which an object’s mass acts.