Forces

Question 1

Newton’s third law of motion

Answer 1

• every force has an equal and opposite reaction force
• a person exerts a contact force on a chair downwards
• the chair exerts an equal contact force on the person upwards
• all forces are measured in newtons

Question 2

Newton’s first law of motion

Answer 2

Balanced forces remain stationary or continue at the same speed

Question 3

Weight

Answer 3

• attractive force that acts on any mass towards the centre of a planet

Question 4

Friction

Answer 4

Always opposes the motion of an object
E.g. Air resistances, drag and contact friction
Can be reduced with lubrication, aerodynamics and streamlining
Can cause energy to change into heat and sound

Question 5

Resultant forces

Answer 5

If the forces balance the object is in equilibrium and the resultant force is zero
If the resultant force is zero there is no acceleration
If the forces are not balanced, the resultant force acts
A resultant force will cause an objects speed to change in the direction of the resultant force

Question 6

Newton’s second law of motion

Answer 6

If forces are not balanced the resultant force acts
F = m X a 
F= resultant force (N)
M = mass (Kg)
A = Acceleration (m/s^2)

Question 7

Gravitational force

Answer 7

Weight = mass X g
G = acceleration of gravity(m/s^2)

Question 8

Hooke’s law

Answer 8

Investigates how much an object extends 
F = ke
F= force applied(n)
E = extension force (m)
K = Spring constant (N/M)