9. Impulse & Newton's 2nd + 3rd Laws

Question 1

What is Newton’s 2nd Law?

Answer 1

AKA The Law of Momentum

In order to change the momentum of a system, we need to apply a force over a period of time.

Question 2

What is an Impulse?

Answer 2

A change in momentum, is produced by an Impulse

• Impulse = Force (F) x time (t)
• Units: N*s

Question 3

How can the Impusle formula be rewritten?

Answer 3

Impulse = ∆M
I = M2 - M1
Ft = mv2 - mv1

Question 4

Why is Newton’s 2nd Law (Law of Momentum) often reffered to (incorrectly) as the Law of Acceleration?

Answer 4

● Newton’s Second Law is The Law of Momentum

• “The rate of change of momentum of a body (or the acceleration for a body of constant mass) is proportional to the force causing it and the change takes place in the direction in which the force acts.”

● However, often referred to as the Law of Acceleration

• A force applied to a body causes an acceleration of that body of a magnitude proportional to the force, in the direction of the force, and inversely proportional to the body’s mass. Newton’s Second Law Re-Examined

Question 5

Why is Newton’s Second Law referred to as the Law of Momentum AND the Law of Acceleration?

be able to explain what is happening in words for the final

Answer 5

Ft = mv2 - mv1
F = mv2 -mv1 / t
F = m(v2- v1) / t
F =ma

Question 6

According to Newton’s 2nd Law, is it possible to blow your own sail?

Answer 6

According to Newton’s Second Law, you cannot blow your own sail because doing so would not create a net external force; instead, the action of blowing would generate an equal and opposite reaction, leaving you stationary. The force you exert by blowing would only push you backward, not propel the sail forward.

Question 7

What is Newton’s Third Law?

Answer 7

The Law of Action and Reaction

For every action, there is an equal and opposite reaction

For every force applied by one body on a second, the second body applies an equal and opposite force on the first

Question 8

According to Newton’s 3rd Law, is it possible to blow your own sail?

Answer 8

No, becuase a reaction force will cancel out the force generated by the fan.

However, it is possibel to move a boat using a fan inside the boat but it does so contradicting Newton’s law and does so very slowly/uncontrollably

Question 9

Class Summary

Newton’s laws of motion are three physical laws that, together, laid the foundation for classical mechanics. They describe the relationship between a body and the forces acting upon it, and its motion in response to those forces

How do they connect to each other?

Answer 9