Unit 5: Free to move?

Question 1

Newton’s First Law

Answer 1

• Law of Inertia
• Every object will remain at rest or in constant
  uniform motion in a straight line unless compelled to change its state by the action of an external force. (unbalanced force).

Question 2

Newton’s Second Law

Answer 2

• Fnet = MA
• Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated), the greater force needed (to accelerate it)

Question 3

Newton’s Third Law

Answer 3

• Action -> Reaction
• For every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exerts an equal and opposite force on object A.

Question 4

Momentum

Answer 4

• momentum = mass x velocity

- change in momentum = time x force

Question 5

Drag

Answer 5

• When objects move through a fluid, the substance exerts a retarding force on the moving object
• Depends on velocity

Question 6

Falling in a vacuum

Answer 6

• In a vacuum there is no air resistance

- The mass is only accelerated by its weight

Question 7

Terminal Velocity

Answer 7

• Drag = Gravitational Force

- No further acceleration (maximum velocity)

Question 8

System

Answer 8

• Total Momentum in a closed system must stay constact

- The system is ‘closed’ as long as no external forces act on it.

Question 9

Thrust

Answer 9

• A reaction force described quantitatively by Newton’s third law.
• When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction on that system.
• Eg: Rocket

Question 10

Law of Conservation of Momentum

Answer 10

• The momentum of an isolated system remains constant. Momentum is therefore said to be conserved over time; that is, momentum is neither created nor destroyed, only transformed or transferred from one form to another.