- Sir Isaac Newton published his three laws of motion in 1687 in his book "Philosophiae Naturalis Principia Mathematica", establishing the laws of motion that describe how objects move. - Newton's second law states that the acceleration of an object depends on the net force acting on the object and its mass, such that acceleration is directly proportional to net force and inversely proportional to mass. - The equation for Newton's second law is: Force = mass x acceleration (F=ma), where the SI unit for force is the Newton.

1. ANCY C SIMON
Physical Science Optional
Register Number- 13971004

3. Background
Sir Isaac Newton (1643-1727) an English scientist and
mathematician famous for his discovery of the law of
gravity also discovered the three laws of motion. He
published them in his book Philosophiae Naturalis
Principia Mathematica (mathematic principles of natural
philosophy) in 1687. Today these laws are known as
Newton’s Laws of Motion and describe the motion of all
objects on the scale we experience in our everyday
lives.

4. Sir Issac Newton
“If I have ever made any valuable discoveries, it has
been owing more to patient attention, than to
any other talent.”
-Sir Isaac Newton

5. Force
• Force is an action that can change motion.
– A force is what we call a push or a pull, or any
action that has the ability to change an object’s
motion.
– Forces can be used to increase the speed of an
object, decrease the speed of an object, or change
the direction in which an object is moving.

6. Newton's Second Law
• If you apply more force to an object, it accelerates at
a higher rate.

7. Newton's Second Law
• If the same force is applied to an object with greater
mass, the object accelerates at a slower rate because
mass adds inertia.

8. According to Newton, an object will only accelerate if
there is a net or unbalanced force acting upon it. The
presence of an unbalanced force will accelerate an
object - changing its speed, its direction, or both its
speed and direction.

9. Newton's second law of motion :
Newton's second law of motion pertains to the
behavior of objects for which all existing forces are
not balanced. The second law states that the
acceleration of an object is dependent upon two
variables - the net force acting upon the object and
the mass of the object

10. The acceleration of an object depends directly upon
the net force acting upon the object, and inversely
upon the mass of the object.
As the force acting upon an object is increased, the
acceleration of the object is increased.
As the mass of an object is increased, the acceleration
of the object is decreased.

11. Newton's second law of motion
can be formally stated as follows:
The acceleration of an object as produced by a net
force is directly proportional to the magnitude of the
net force, in the same direction as the net force, and
inversely proportional to the mass of the object.

12. Newton’s Second Law of Motion
In other words…
How much an object accelerates depends on
the mass of the object and how much force is
applied to it.
The equation for this is:
Force = mass x acceleration
F=ma

13. Units of Force = Newton (N)
SI units for mass is kg
SI units for acceleration is m/s2
The unit of force is Newton(N)
1 Newton (N) = 1kg . m/s2
 One Newton (1N) is the force required to produce
an acceleration of 1m/s on a body of mass 1kg.

14. Newton's Second Law
Three forms of the second law:

15. Newton’s Second Law of Motion
If a baseball is thrown at 150 m/s2 and its mass is
0.50 kg what force is necessary to change its
direction?
a = 150 m/s2
m = 0.50 kg
F = ?
F = ma
F = (0.50 kg)(150 m/s2 )
F = 75 kg m/s2
= 75 N

16. 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 = ma
98 N = 10 kg x 9.8 m/s/s
F = ma
9.8 N = 1 kg x 9.8
m/s/s

17. Applications of 2nd Law

18. Check Your Understanding
 Determine the accelerations that result when a 12-N net force is applied to
a 3-kg object and then to a 6-kg object.
 A net force of 15 N is exerted on an encyclopedia to cause it to accelerate
at a rate of 5 m/s2. Determine the mass of the еncyclopedia.
 Suppose that a sled is accelerating at a rate of 2 m/s2. If the net force is
tripled and the mass is doubled, then what is the new acceleration of the
sled?
 Suppose that a sled is accelerating at a rate of 2 m/s2. If the net force is
tripled and the mass is halved, then what is the new acceleration of the
sled?

19. Your answers have to be:
• 1. A 3-kg object experiences an acceleration of 4
m/s2. A 6-kg object experiences an acceleration of 2
m/s2.
 2. Use F= m a with F = 15 N and a = 5 m/s2
So (15 N) = (m) x (5 m/s2)
And m = 3.0 kg
 3. Answer: 3 m/s2
The original value of 2 m/s2 must be multiplied by
3 (since a and F are directly proportional) and divided
by 2 (since a and m are inversely proportional)
 4. Answer: 12 m/s2
The original value of 2 m/s2 must be multiplied by
3 (since a and F are directly proportional) and divided
by 1/2 (since a and m are inversely proportional)

20. Thank You