3.5: Newton's Law of Motion, F

Question 1

Define: Newton’s first law

Answer 1

A body remains at rest/continue to move in a straight line at a constant velocity unless an external force acts on it (Inertia)

Question 2

Define: Newton’s second law

Answer 2

Resultant force is proportional to the rate of change of momentum of the object, which is directly proportional to the object (F = ma)

Question 3

Define: Newton’s third law

Answer 3

If object A exerts a force on object B, then object B will exert an equal and opposite force on object A

Question 4

What is the principle of conservation of momentum

Answer 4

Momentum is always conserved = the total momentum before a collision is always equal to the total after (assuming there are no external forces)

Question 5

What is the difference between an elastic and inelastic collision

Answer 5

-Elastic = kinetic energy is conserved
no loss of energy
- Inelastic = some kinetic energy is loss. converted into other forms

Momentum is always conserved

Question 6

Define: Impulse

Answer 6

Change in momentum
(Impulse = F x ‘change in’ t)
(Average force x time)

Question 7

What does the area under a force-time graph give

Answer 7

F x t = impulse

Question 8

Give 3 safety features of a car that are designed to protect passengers in the event of a crash and briefly explain

Answer 8

• Crumple zone : Absorbs Ek + increase time taken to slow down
• Air bags : Makes Passengers slow down gradually + prevent touching dash
• Seat belts : Hold wearer in place + absorbs some Ek