#### Laws of Motion

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Transcript Laws of Motion

LAWS OF MOTION
Chapter 11
Newton’s First Law
an object at rest remains at rest and
an object in motion maintains its velocity (stays in
motion) unless it experiences an unbalanced
force (outside force).
Aka Law of Inertia
INERTIA
tendency of an object to resist being moved or
if object is moving, resist a change in speed or
direction until an outside force acts on object.
All objects resist changes in motion
Less mass, less inertia
More mass, more inertia
Chapter 11
INERTIA EXAMPLE
Seat belts and car seats provide protection.
• Because of inertia, you slide toward the side of a car
when the driver makes a sharp turn.
• When the car you are riding in comes to a stop, your
seat belt and the friction between you and the seat stop
your forward motion.
WHY WEAR A SEATBELT?
SEATBELT IN THE BACKSEAT?
Newton’s Second Law
unbalanced force acting on an object equals object’s mass
times its acceleration.
Force = mass acceleration
SI Unit:
newtons (N)
1 N = 1 kg 1 m/s2
F
m a
Zookeepers lift a stretcher that holds a sedated lion. The total
mass of the lion and stretcher is 175 kg, and the lion’s upward
acceleration is 0.657 m/s2. What is the unbalanced force
necessary to produce this acceleration of the lion and the
stretcher?
GIVEN:
WORK:
F=?
m= 175 kg
a = 0.657 m/s2
F = ma
F
ma
F = (175 kg) (0.657 m/s2)
F = 115 N
What is the net force necessary for a 1.6 x 103 kg automobile to
accelerate forward at 2.0 m/s2?
GIVEN:
WORK:
F=?
m= 1.6 x 103 kg
a = 2.0 m/s2
F = ma
F
ma
F = (1.6 x 103 kg) (2.0 m/s2)
F = 3.2 x 103 N
A baseball accelerates downward at 9.8 m/s2. If the gravitational force
is the only force acting on the baseball and is 1.4 N, what is the
baseball’s mass?
GIVEN:
WORK:
F = 1.4 N
m= ?
a = 9.8 m/s2
m = F/a
F
ma
m = 1.4 N / 9.8 m/s2
m = 0.14 kg
A sailboat and its crew have a combined mass of 655 kg. Ignoring
frictional forces, if the sailboat experiences a net force of 895 N
pushing it forward, what is the sailboat’s acceleration?
GIVEN:
WORK:
F = 895 N
m= 655 kg
a=?
a = F/m
F
ma
a = 895 N / 655 kg
a = 1.37 m/s2