7. Laws of motion and momentum

Question 1

Define Newton’s first law of motion

Answer 1

An object will remain at rest or continue to move with constant velocity unless acted upon by a resultant force

Question 2

Define Newton’s third law of motion

Answer 2

When two objects interact, they exert equal and opposite forces on each other

Question 3

Define Newton’s second law of motion

Answer 3

The net (resultant) force acting on an object is directly proportional to the rate of change of its momentum, and is in the same direction

Question 4

What is the equation for momentum?

Answer 4

p = mv

p = momentum / Kgms^-1
m = mass / Kg
v = velocity / ms^-1

Question 5

What is the principle of conservation of momentum?

Answer 5

For a system of interacting objects, the total momentum in a specified direction remains constant, as long as no external forces act on the system

Question 6

What is not conserved in an inelastic collision?

Answer 6

Total kinetic energy

Question 7

What is the relationship between Net force and rate of change of momentum and what equation can we derive from this?

Answer 7

Net force is directly proportional to the rate of change of momentum

F = k ∆p / ∆t
k = 1N
F = ∆p / ∆t

Question 8

Derive F = ma

Answer 8

F = ∆p / ∆t
F = mv-mu / t
F = m(v-u/t)
F = ma

Question 9

Define Impulse of a force

Answer 9

The product of force and the time for which this force acts on an object

Question 10

What is the equation for impulse of a force?

Answer 10

Impulse = F∆t
(impulse = change in momentum)

Question 11

What is the area of a force time graph (if the force is constant)

Answer 11

Impulse