This document summarizes Newton's three laws of motion. The first law states that an object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force. The second law states that force equals mass times acceleration. The third law states that for every action there is an equal and opposite reaction. Examples are provided to illustrate each law, including how friction causes an object in motion to come to rest due to an unbalanced force. Check questions are included to test understanding of applying the second law calculations.

1. Vidya Bharti EducationalVidya Bharti Educational
InstitutionsInstitutions

3. Newton’s Laws of MotionNewton’s Laws of Motion
 11stst
LawLaw –– An object at rest will stay at rest,An object at rest will stay at rest,
and an object in motion will stay inand an object in motion will stay in
motion at constant velocity, unless actedmotion at constant velocity, unless acted
upon by an unbalanced forceupon by an unbalanced force..
 22ndnd
LawLaw – Force equals mass times– Force equals mass times
acceleration.acceleration.
 33rdrd
LawLaw – For every action there is an– For every action there is an
equal and opposite reaction.equal and opposite reaction.

4. 11stst
Law of MotionLaw of Motion
(Law of Inertia)(Law of Inertia)
An object at rest will stay atAn object at rest will stay at
rest, and an object in motionrest, and an object in motion
will stay in motion atwill stay in motion at
constant velocity, unless actedconstant velocity, unless acted
upon by an unbalanced forceupon by an unbalanced force..

5.  There are four main types of friction:There are four main types of friction:
 Sliding friction:Sliding friction: ice skating
 Rolling friction:Rolling friction: bowling
 Fluid friction (air or liquid):Fluid friction (air or liquid): air or water resistance
 Static friction:Static friction: initial friction when moving an
object
What is unbalanced force that acts on an object in motion?What is unbalanced force that acts on an object in motion?

6. ExampleExample -Slide a book-Slide a book
across a table andacross a table and
watch it slide to a restwatch it slide to a rest
position. The bookposition. The book
comes to a restcomes to a rest
because of thebecause of the
presencepresence of a force -of a force -
that force being thethat force being the
force of friction -force of friction -
which brings the bookwhich brings the book
to a rest position.to a rest position.

7.  In the absence of a force of friction, the bookIn the absence of a force of friction, the book
would continue in motion with the same speedwould continue in motion with the same speed
and direction - forever! (Or at least to the endand direction - forever! (Or at least to the end
of the table top.)of the table top.)

8. Newtons’s 1Newtons’s 1stst
Law and YouLaw and You
Don’t let this be you. Wear seat belts.Don’t let this be you. Wear seat belts.
Because of inertia, objects (including you) resist changesBecause of inertia, objects (including you) resist changes
in their motion.in their motion.

9. 22ndnd
LawLaw

10. 22ndnd
LawLaw
The net force of an object isThe net force of an object is
equal to the product of its massequal to the product of its mass
and acceleration, orand acceleration, or F=ma.F=ma.

11. 22ndnd
LawLaw
 When mass is in kilograms and acceleration isWhen mass is in kilograms and acceleration is
in m/s/s, the unit of force is in newtons (N).in m/s/s, the unit of force is in newtons (N).
 One newton is equal to the force required toOne newton is equal to the force required to
accelerate one kilogram of mass at oneaccelerate one kilogram of mass at one
meter/second/second.meter/second/second.

12. 22ndnd
Law (F = m x a)Law (F = m x a)
 How much force is needed to accelerate a
1400 kilogram car 2 meters per second/per
second?
 Write the formulaWrite the formula
 F = m x a
 Fill in given numbers and unitsFill in given numbers and units
 F = 1400 kg x 2 meters per second/second
 Solve for the unknownSolve for the unknown

2800 kg-meters/second/second or 2800 N

13. If mass remains constant, doubling the acceleration, doubles the force. If force remains
constant, doubling the mass, halves the acceleration.

14. Newton’s 2nd
Law proves that different masses
accelerate to the earth at the same rate, but with
different forces.
• We know that objects
with different masses
accelerate to the
ground at the same
rate.
• However, because of
the 2nd
Law we know
that they don’t hit the
ground with the same
force.
F = maF = ma
98 N = 10 kg x 9.8 m/s/s98 N = 10 kg x 9.8 m/s/s
F = maF = ma
9.8 N = 1 kg x 9.89.8 N = 1 kg x 9.8
m/s/sm/s/s

15. Check Your UnderstandingCheck Your Understanding
 1. What acceleration will result when a 12 N net force applied to a 3 kg1. What acceleration will result when a 12 N net force applied to a 3 kg
object? A 6 kg object?object? A 6 kg object?
 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s22
..
Determine the mass.Determine the mass.
 3. How much force is needed to accelerate a 66 kg skier 1 m/sec/sec?3. How much force is needed to accelerate a 66 kg skier 1 m/sec/sec?
 4. What is the force on a 1000 kg elevator that is falling freely at 9.84. What is the force on a 1000 kg elevator that is falling freely at 9.8
m/sec/sec?m/sec/sec?

16. Check Your UnderstandingCheck Your Understanding
 1. What acceleration will result when a 12 N net force applied to a 3 kg object?1. What acceleration will result when a 12 N net force applied to a 3 kg object?
12 N = 3 kg x 4 m/s/s12 N = 3 kg x 4 m/s/s
 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s22
. Determine the. Determine the
mass.mass.
16 N = 3.2 kg x 5 m/s/s16 N = 3.2 kg x 5 m/s/s
 3. How much force is needed to accelerate a 66 kg skier 1 m/sec/sec?3. How much force is needed to accelerate a 66 kg skier 1 m/sec/sec?
66 kg-m/sec/sec or 66 N66 kg-m/sec/sec or 66 N
 4. What is the force on a 1000 kg elevator that is falling freely at 9.8 m/sec/sec?4. What is the force on a 1000 kg elevator that is falling freely at 9.8 m/sec/sec?
 9800 kg-m/sec/sec or 9800 N9800 kg-m/sec/sec or 9800 N

18. 33rdrd
LawLaw
 For every action, there is anFor every action, there is an
equal and opposite reaction.equal and opposite reaction.

19. 33rdrd
LawLaw
According to Newton,According to Newton,
whenever objects A andwhenever objects A and
B interact with eachB interact with each
other, they exert forcesother, they exert forces
upon each other. Whenupon each other. When
you sit in your chair,you sit in your chair,
your body exerts ayour body exerts a
downward force on thedownward force on the
chair and the chairchair and the chair
exerts an upward forceexerts an upward force
on your body.on your body.

20. 33rdrd
LawLaw
There are two forcesThere are two forces
resulting from thisresulting from this
interaction - a force oninteraction - a force on
the chair and a force onthe chair and a force on
your body. These twoyour body. These two
forces are calledforces are called actionaction
andand reactionreaction forces.forces.

21. 33rdrd
LawLaw
 Example :Consider theExample :Consider the
motion of a car on themotion of a car on the
way to school. A car isway to school. A car is
equipped with wheelsequipped with wheels
which spin backwards.which spin backwards.
As the wheels spinAs the wheels spin
backwards, they grip thebackwards, they grip the
road and push the roadroad and push the road
backwards.backwards.

22. Thank youThank you
EveryoneEveryone
 Get more knowledgeGet more knowledge
with VBEI.with VBEI.
 Follow us:Follow us:
https://www.facebook.com/ggnVidyaBharti/?fref=https://www.facebook.com/ggnVidyaBharti/?fref=t