Newton’s Second Law of Motion

NEWTON’S SECOND LAW OF MOTION

NEWTON’S SECOND LAW OF MOTION Objectives:You will be able to:1. State Newton’s second law and

describe how it is related to motion2. Explain how Newton’s second law

describes how acceleration is directly proportional to the net force, and inversely proportional to mass.

3. Solve problems using Newton’s second law

RECALL THAT:1)An unbalanced force can cause an object at rest to

move , changing its velocity creating an aceleration (rf ch2,

section 2)

2) An object at rest or moving at constant speed will remain if

the net force is equal to zero

IN OTHER WORDS

NEWTON’S SECOND LAW OF MOTIONLook at the figures and

answer the below questions:

- Which figure (s) represent accelerating objects? In which direction.

- Which figure represent the object having the highest acceleration?

- Conclude.

FORCE AND ACCELERATION

Look at the following diagrams and answer the below questions:1. Which objects are accelerating?

Which objects are not accelerating?

---------------------------------------------2. Which object are subject to an

unbalanced force?---------------------------------------------3. Which objects are subject to a net

force equal to zero?---------------------------------------------4. Conclude----------------------------------------------------

CONCLUSION1. A force can accelerate an object in the

same direction of the force.2. Acceleration is directly proportional to

force( example: if force is multiplied by two, acceleration would be multiplied by two).

Application:3. A net force of 200 N to the right

accelerates an object of 2m/s² .Find the acceleration of this object if:a. Net force = 400 to the leftb. Net force= 300 N to the right

2. For each of the following, state if the object would be accelerating. If yes, write in which direction.

a. Object 1: F1= 400 N upward, F2= 600 N downward.

b. Object 2: F1= 400 N upward, F2= 400 N downward.

c. Object 3; F1= 400 N upward, F2= 400 N downward, F3= 200 N to the left.

NEWTON’S SECOND LAW OF MOTION

Mass and acceleration

Look at the figure below

Which object would be have a higher acceleration if they are subject to the same force?

----------------------------------Conclude----------------------------------

CONCLUSION Objects with higher masses would have

lower acceleration if subject to the same force. This can be explained by the fact that big masses have high inertia so they have greater tendency to resist any change in motion. (Rf.to chapter 2 section 3)

Acceleration is inversely proportional to the mass ( example if mass is multiplied by three, acceleration would be divided by three).

NEWTON’S SECOND LAW OF MOTIONWe can summarize that acceleration is: Directly proportional to the force applied Inversely proportional to the mass of the

object.In other words, we can write:

Acceleration(m/s²)= force (N)/mass (kg)

NEWTON’S SECOND LAW OF MOTION

• Newton’s second law of motion states that the acceleration of an object is in the same direction as the net force on the object, and that the acceleration can be calculated from the following equation:

NEWTON ‘S SECOND LAW OF MOTION

Application : Solve questions 1- 9 from the worksheet

Answer:Acceleration= force/mass= 50/1,000=

0.05 n/s²

Now can you calculate the acceleration of the car in the figure at the right ?

DO NOT FORGET If forces are

balanced (net force =0),an object at rest stays at rest, an object with a constant velocity keeps its constant velocity. (acceleration= 0)

This is Newton’s first Law of Motion.

If Forces are unbalanced (net force=0), an object will change aits velocity and have an acceleration in the same as the direction of the force and:

Acceleration=Force(N) (m/s²) Mass (kg)

FOR NEXT TIME Solve questions

TB page: - 69 no:1-4 - 74 no: 1,2,6 &7 Download

powerpoint presentation from wikispaces

System wide quiz 2 on Sunday 20/11/2011

Lessons included:Ch: 1: section 1.3Ch.2: section 2.1

section 2.2

Good Luck !!!