Mechanics

Question 1

Assumption: Particle

Answer 1

• dimensions of the object are negligible (dimensions can be ignored)
• mass of object is concentrated at a single point
• rotational forces/air resistance is negligible (can be ignored)

Question 2

Assumption: Rod e.g. pole / beam

Answer 2

• all dimensions except one are negligible (dimensions can be ignored except the length)
• mass is concentrated along a line
• no thickness
• rigid (doesn’t bend or buckle)

Question 3

Assumption: Lamina e.g. sheet of paper

Answer 3

• object with area but negligible thickness (no thickness)

- mass is distributed across a flat surface

Question 4

Assumption: Uniform body

Answer 4

• mass is distributed evenly

- mass of object is concentrated in the centre of the body - the centre of mass

Question 5

Assumption: Light object e.g. string / pulley

Answer 5

• mass of the object is small, relative to masses of other objects
• treat as having zero mass