Transcript Newton`s 2nd Law

Newton’s 2nd Law Notes
Topics
• What happens when the net force is not
ZERO.
• Newton’s 2nd Law
• Relationship between Force, Mass and
Acceleration.
• Solve motion practice problems using
Newton’s 2nd Law.
We Have Already Learned
• Objects stay in the state of
motion they are already at
unless they are acted on by an
UNBALANCED FORCE.
• So what happens when objects
are acted on by an
UNBALANCED FORCE?
When Net Force is NOT ZERO
• the force is UNBALANCED
• The object the
UNBALANCED Force acts on
will ACCELERATE in the
direction of the force.
Newton’s 2nd Law is
• FORCE=MASS x ACCELERATION
• OR
• F=ma
F=ma so
• a= F/m
• m= F/a
Force Mass Acceleration Relationships
As Force Goes Up Acceleration
Goes Up
2N
2
a=2m/s
1kg
a=4m/s2
1kg
4N
Force Mass Acceleration Relationships
Force and Acceleration are
Directly Related This Means
As One Goes Up So Does The
Other.
As One Goes Down So Does The
Other.
Force Mass Acceleration Relationships
As Mass Goes Up Acceleration
• Goes Down
a=
2
2m/s
a=
1m/s2
1kg
2 kg
2N
2N
Force Mass Acceleration Relationships
Mass and Acceleration Are
• Inversely Related
• This means as one goes Up the
other goes Down.
Motion Practice Problem
If a 10 Newton Force acts on a
5kg Box at what rate will it
accelerate?
• F= 10 N, m=5 kg, a=?
• F=ma or a = F/m
• 10N= 5kg x a
• a= 10N/5kg
• a=2m/s2
Practice Problem 2
Acceleration of a 1kg box on a Table
Step 1- Label All Forces
10 N
20 N Push Force
5 N Friction
1 kg
10 N
Step 2 Find Net Force on x and y axis
10 N
20 N
1 kg
5N
Y axis = 10N-10N= 0N 10 N
X axis= 20N- 5N = 15N
Box will accelerate in the x direction
because force is Unbalanced.
Step 3 Calculate Acceleration
F= ma and a= F/m
a= 15N/1kg =
15 N
2
15m/s
Net Force
Diagram
1 kg
15 Newtons is used because that is
the Net Force