Kinematics - Topic 7

Question 1

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses a particle?

Answer 1

• Mass of the object is concentrated at a single point
• Rotational forces and air resistance can be ignored

Question 2

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses a rod?

Answer 2

• Mass is concentrated along a line
• No thickness
• Rigid

Question 3

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses lamina?

Answer 3

• Mass is distributed across a flat surface

Question 4

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses a uniform body?

Answer 4

• Mass of the object is concentrated at a single point at the geometrical centre of the body - the centre of mass

Question 5

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses a light body?

Answer 5

• Treat object as having zero mass
• Tension the same at both ends of a light string

Question 6

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses an inextensible string?

Answer 6

• Acceleration is the same in objects connected by a taut inextensible string

Question 7

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses a smooth surface?

Answer 7

• Assume that there is no friction between the surface and any object on it

Question 8

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses a rough surface?

Answer 8

• Objects in contact with the surface experience a frictional force if they are moving or are acted on by a force

Question 9

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses a wire?

Answer 9

• Treated as one-dimensional

Question 10

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses a smooth and light pulley?

Answer 10

• Pulley has no mass
• Tension is the same on either side of the pulley

Question 11

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses a bead?

Answer 11

• Moves freely along a wire or string
• Tension is the same on either side of the bead

Question 12

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses a peg?

Answer 12

• Dimensionless and fixed
• Can be rough or smooth as specified in question

Question 13

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses air resistance?

Answer 13

• Usually modelled as being negligible

Question 14

Year 1 - Chapter 8.2

What modelling assumption is made if the model uses gravity?

Answer 14

• Assume that all objects with mass are attracted towards the Earth
• Earth’s gravity is uniform and acts vertically downwards
• g is constant and is taken as 9.8ms⁻², unless otherwise stated in the question