Download Newton`s Laws of Motion

Newton’s 2nd Law of Motion
Newton’s Second Law of Motion
• What the law states: The unbalanced
net force acting on an object is equal to
the product of its mass and its acceleration
- OR Force
(in Newtons)
Mass (in kg)
F = ma
Acceleration
(in m/s2)
In other words:
Force equals mass times acceleration
• Describes how a force applied to an
object’s mass affects its acceleration
Standard Units
• Mass (m) in kg
• Acceleration (a) in m/s2
• Force (F) in NEWTONS (N)
– equal to the force required to accelerate
1 kilogram of mass 1 m/s2
• Force is a VECTOR and
requires a direction!!
F
m
a
Calculation of Force
How much force is needed to accelerate a 1400 kg
car 2.0 m/s2 forward?
Given:
m = 1400 kg
a = 2.0 m/s2
Looking for?
Force (F)
Relationship:
F = ma
Solution:
F = 1400 kg x 2.0 m/s2
= 2800 kg • m/s2
= 2800 N FORWARD!!
What acceleration will result when a 12 N net force
applied to the left on a 3.0 kg object?
Given:
F = 12 N
m = 3.0 kg
Looking for?
acceleration (a)
Relationship:
a=F
2 left
=
4.0
m/s
m
Solution:
a = 1212
kgN· m/s2
3.0 kg
A net force of 16 N causes a mass to accelerate
south at a rate of 5.0 m/s2. Determine the mass.
Given:
F = 16 N
a = 5.0 m/s2
Looking for?
mass (m)
Relationship:
m=F
=
3.2
kg
a
Solution:
m = 16 16
kg N
· m/s2
5.0 m/s2
Force, Mass and Acceleration
A constant force
applied to greater
mass causes less
acceleration.
Same F, bigger m, smaller a
Doubling the mass,
halves the
acceleration.
The acceleration of an
object is inversely
proportional to its
mass
Force, Mass and Acceleration
More force on a
constant mass causes
more acceleration.
Doubling the force,
doubles the
acceleration.
The acceleration of an
object is directly
proportional to the
force acting on it
PRACTICE
• HOMEWORK TIME!! Force
Calculations