Coach Dave Edinger
J. C. Booth Middle School
Physical Science (8A)
Newton’s Second Law
Newton’s 1st law REVIEW
Summarize what the law states.
What does an object at rest need for it to move?
What is another name for Newton’s first law of motion?
What is inertia?
What causes a moving object to stop moving?
The (more/less) mass an object has, the harder it is to move.
The (more/less) mass an object has, the easier it is to move.
NEWTON’S second law
The acceleration of an object depends on the
mass of the object and the amount of force
applied.
VOLUNTEERS!!!!!
TWO “pushers” of similar size
ONE small 8th grader
ONE big 8th grader
Part 1: Acceleration depends on mass
Acceleration of an object decreases as its
mass increases.
Acceleration of an object increases as its
mass decreases.
Which would
be easier to
push?
WHY?
Part 2: Acceleration depends on force
Acceleration of an object increases as the
force on it increases
Acceleration of an object decreases as the
force on it decreases
VOLUNTEERS!!!!!
ONE to sit in chair
ONE to push chair
Newton’s law with MATH
Formula: Force = mass • acceleration
F
m a
UNITS 
accleration: m/s²
force:
N
mass:
kg
(meters per second squared)
(Newtons)
(kilograms)
Tricky…tricky….

You don’t use Newtons to find
acceleration in this formula
1 N = 1 kg∙m/s²
So…4 N = 4 kg∙m/s²
And….500 N = 500 kg∙m/s²
And 395 N = ?
Newton and math example
Mass of apple: 0.102kg
Force: 1N
What is the acceleration?
Newton and math example
Mass of apple: 0.102kg
Force: 1N
What is the acceleration?
a = F/m
Newton and math example
Mass of apple: 0.102kg
Force: 1N
What is the acceleration?
a = F/m
a = 1N / 0.102kg
Newton and math example
Mass of apple: 0.102kg
Force: 1N
What is the acceleration?
a = F/m
a = 1N / 0.102kg
a= 1 kg∙m/s² / 0.102kg
a= 9.8 m/s2
Practice
What is the acceleration of a 7kg mass if a
force of 68.6 N is used to move the mass?
a=F/m
Practice
What is the acceleration of a 7kg mass if a
force of 68.6 N is used to move it toward
earth?
a=F/m
a = 68.6 N / 7 kg
Practice
What is the acceleration of a 7kg mass if a
force of 68.6 N is used to move it toward
earth?
a=F/m
a = 68.6 N / 7 kg
a = 68.6 kg • m/s2 / 7 kg
Practice
What is the acceleration of a 7kg mass if a
force of 68.6 N is used to move it toward
earth?
a=F/m
a = 68.6 N / 7 kg
a = 68.6 kg • m/s2 / 7 kg
a = 9.8 m/s2
Practice
What is the acceleration of a 7kg mass if a
force of 68.6 N is used to move it toward
earth?
a=F/m
a = 68.6 N / 7 kg
a = 68.6 kg • m/s2 / 7 kg
a = 9.8 m/s2
Practice
What is the acceleration of a 7kg mass if a
force of 68.6 N is used to move it toward
earth?
a=F/m
a = 68.6 N / 7 kg
a = 68.6 kg • m/s2 / 7 kg
a = 9.8 m/s2
Challenge question
What force is necessary to accelerate a
1,250kg car at a rate of 40 m/s² ?
Challenge question
What force is necessary to accelerate a
1,250kg car at a rate of 40 m/s² ?
F = ma
Challenge question
What force is necessary to accelerate a
1,250kg car at a rate of 40 m/s² ?
F = ma
F = 1250 kg • 40 m/s2
Challenge question
What force is necessary to accelerate a
1,250kg car at a rate of 40 m/s² ?
F = ma
F = 1250 kg • 40 m/s2
F = 50,000 kg • m/s2
Challenge question
What force is necessary to accelerate a
1,250kg car at a rate of 40 m/s² ?
F = ma
F = 1250 kg • 40 m/s2
F = 50,000 kg • m/s2
F = 50,000 N
Another challenging question
Zookeepers carry a stretcher that holds a sleeping
lion. The total mass of the lion and the stretcher
is 175 kg. The lion’s forward acceleration is 2
m/s². What is the force necessary to produce this
acceleration?
Another challenging question
Zookeepers carry a stretcher that holds a sleeping
lion. The total mass of the lion and the stretcher
is 175 kg. The lion’s forward acceleration is 2
m/s². What is the force necessary to produce this
acceleration?
F = ma
Another challenging question
Zookeepers carry a stretcher that holds a sleeping
lion. The total mass of the lion and the stretcher
is 175 kg. The lion’s forward acceleration is 2
m/s². What is the force necessary to produce this
acceleration?
F = ma
F = 175 kg • 2 m/s2
Another challenging question
Zookeepers carry a stretcher that holds a sleeping
lion. The total mass of the lion and the stretcher
is 175 kg. The lion’s forward acceleration is 2
m/s². What is the force necessary to produce this
acceleration?
F = ma
F = 175 kg • 2 m/s2
F = 350 kg • m/s2
Another challenging question
Zookeepers carry a stretcher that holds a sleeping
lion. The total mass of the lion and the stretcher
is 175 kg. The lion’s forward acceleration is 2
m/s². What is the force necessary to produce this
acceleration?
F = ma
F = 175 kg • 2 m/s2
F = 350 kg • m/s2
F = 350 N