Download Newton`s Laws of Motion

Newton’s Laws of Motion
Newton’s First Law of Motion – Law of Inertia
 An object at rest will remain at rest, an object in motion will remain in
motion at constant velocity unless acted upon by an unbalanced force.
 For an object to start moving, a force greater than the force of static
friction must be applied to it. To keep the object in motion, a force at
least as strong as friction must be applied continuously. Objects stop
moving because friction or some other force acts on them.
 Inertia is the tendency of an object to resist a change in motion. The
greater the mass of an object, the greater its inertia and the greater the
force required to change its motion.
 Terminal velocity occurs when the forces of gravity and air
resistance are balanced and the object falls at a constant velocity.
Newton’s Second Law of Motion
 An object’s acceleration depends on its mass and on the net force
acting on it.
 The direction of acceleration is the same as the direction of the net
force.
 The formulas are:
acceleration = net force / mass
force = mass x acceleration
mass = net force / acceleration
 Acceleration is measured in m/s2.
 Mass is measured in kg.
 Force is measured in N.
 Acceleration is affected by 2 factors:
1. the size of the force
2. the mass of the object
 The larger the force acting on an object, the greater the acceleration of
the object.
 The larger the object’s mass, the greater the force needed to give it the
same acceleration.
 Circular motion is any motion in which an object is moving along a
curved path. An object traveling in a circle is accelerating because it
constantly changes direction. If an object is accelerating, a force must
be acting on it. A force that causes an object to move in a circular path
is a centripetal force. If you could turn off a centripetal force, inertia
would cause the object to fly off in a straight line.
 A satellite is any object in space that orbits a larger object. Satellites
experience centripetal force. Satellites tend to move in a straight line
because of inertia. Gravity is the centripetal force that keeps a satellite
in orbit.
Newton’s 3rd Law of Motion
 If one object exerts a force on another object, then the second object
exerts a force of equal strength and in the opposite direction on the
first object.
 For every action there is an equal and opposite reaction.
 All forces come in pairs called force pairs or action – reaction forces.
Example – A bird flying. The action force is the bird’s wings exerting
a force on the air. The reaction force is the air pushing back on the
bird’s wings that propels the bird forward.
 Action – reaction forces do not cancel out because they act on
different objects.
Momentum
 A characteristic of a moving object that is related to the mass and the
velocity of the object.
 The momentum of a moving object can be determined by multiplying
the object’s mass and velocity.
 The formula is:
P=m x v
 The unit for momentum is kg x m/s.
 Momentum is described by both a direction and a strength. The
momentum of an object is in the same direction as its velocity.
 The more momentum a moving object has, the harder it is to stop.
 The Law of Conservation of Momentum states that in the absence
of outside forces like friction, the total momentum of objects that
interact does not change.