# Newton's Second Law

- Created by: Agata
- Created on: 24-02-16 18:11

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- Newton's Second Law
- Newton's Second Law: The rate of change of the momentum of an object is directly proportional to the net force acting upon it.
- ?p/?t ? F
- mv-mu/ t ? F this gives: m(v-u)/t ? F, hence ma ? F
- Note the proportionality sign. In order to make this an equation, a constant of proportionality k must be introduced.
- This gives Newton's Second Law as ma=kF
- Newton's Second Law: The rate of change of the momentum of an object is directly proportional to the net force acting upon it.
- ?p/?t ? F
- mv-mu/ t ? F this gives: m(v-u)/t ? F, hence ma ? F
- Note the proportionality sign. In order to make this an equation, a constant of proportionality k must be introduced.
- This gives Newton's Second Law as ma=kF

- This gives Newton's Second Law as ma=kF

- Note the proportionality sign. In order to make this an equation, a constant of proportionality k must be introduced.

- mv-mu/ t ? F this gives: m(v-u)/t ? F, hence ma ? F

- ?p/?t ? F

- Newton's Second Law: The rate of change of the momentum of an object is directly proportional to the net force acting upon it.

- This gives Newton's Second Law as ma=kF

- Note the proportionality sign. In order to make this an equation, a constant of proportionality k must be introduced.

- mv-mu/ t ? F this gives: m(v-u)/t ? F, hence ma ? F

- ?p/?t ? F
- One Newton - The force that will give a mass of one kilogram an acceleration of one meter per second each second.
- 1 kg x 1m/s^2 = k x 1N

- Mass - The inertia of an object, or how difficult it is to accelerate the object. Units: kilograms
- Weight - The gravitational force the Earth exerts on an object, pulling it towards the ground. Units= N On Earth W=M x 9.81 m/s^2.
- WORKED EXAMPLE: In an experiment to measure the charge on an electron, an electrical force of 2.8 x 10 ^-8 N is exerted upwards on a charged oil drop of mass 3.0 micro grams. What is the acceleration of the oil drop?
- 1) The mass needs to be in kg. 3.0 micro grams= 3.0 x 10 ^-6 g = 3.0 x 10 ^-9 kg.
- 2) The weight W of the drop is (3.0 x 10^-9) x 9.81= 2.943 x 10^-8 N
- 3) This gives a resultant downward force on the drop as (2.943 x 10^-8 ) - (2.8 x 10^ -8) = 0.143 x 10 ^-8 N.
- 4) F(down) = m x a(down) to get (0.143x 10^-8) = (3.0 x 10^-9) x a
- 5) a (down) = (0.143 x 10^-8)/ (3.0 x 10^-9) = 0.477 m/s^2

- 4) F(down) = m x a(down) to get (0.143x 10^-8) = (3.0 x 10^-9) x a

- 3) This gives a resultant downward force on the drop as (2.943 x 10^-8 ) - (2.8 x 10^ -8) = 0.143 x 10 ^-8 N.

- 2) The weight W of the drop is (3.0 x 10^-9) x 9.81= 2.943 x 10^-8 N

- 1) The mass needs to be in kg. 3.0 micro grams= 3.0 x 10 ^-6 g = 3.0 x 10 ^-9 kg.

- Newton's Second Law: The rate of change of the momentum of an object is directly proportional to the net force acting upon it.

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