Transcript Newton’s Laws

1)
What are Newton’s three Laws of Motion?
2) When do we apply the three Laws of Motion?
 Newton’s first law of motion states that an
object at rest remains at rest and an object in
motion maintains its velocity unless it
experiences an unbalanced force.
 Objects tend to maintain their state of motion.
 Inertia is the tendency of an object to resist
being moved or, if the object is moving, to
resist a change in speed or direction until an
outside force acts on the object.
 Newton’s second law of motion states that the
unbalanced force acting on an object equals the
object’s mass times its acceleration.
 Force equals mass times acceleration.
Force = mass  acceleration
F = ma
 Forces have the ability to accelerate an object.
Force is measured in newtons (N).
1 N = 1 kg  1 m/s2
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Newton’s third law of motion states that for
every action force, there is an equal and
opposite reaction force.
Forces always occur in action-reaction pairs.
Action-reaction force pairs are equal in size and
opposite in direction.
Force pairs do not act on the same object. They
act on two different objects
Which of Newton’s Laws Apply to the following
situations? Discuss with your partners and
prepare to share your answer with the class.
1.
2.
3.
4.
5.
A heavier object is harder to move than a lighter
object.
“Seatbelts save lives.”
When you push on a wall it pushes back with
equal force.
The Voyager spacecrafts, launched in the 1977,
continue to travel deeper into space even though
their jet engines ran out of fuel a long time ago.
A rocket ship launching into space>
Answers can vary:
1)
2nd Law (F=MA) or
1st Law as the more
mass you have the
greater your inertia.
2)
3)
4)
5)
1st Law
3rd Law
1st Law
3rd Law
2. What is the net force on a 2.0 kg weight hanging
motionless on a string? (Hint: acceleration rate
of gravity is 9.8 m/s2
A. 0.0 N
B. 2.0 N
C. 9.8 N
D. 19.6 N
3. When a ball is falling
toward Earth, what is the
reaction force to the pull of
gravity on the ball?
F. air pressure pushing up
on the ball
G. force of the ground
against the ball
H. upward pull of the ball
on Earth
I. pull of gravity on the
ball toward Earth
Answers: 2) D 3) H
1) Which of the following is the cause of an acceleration?
a. speed
b. force
c. inertia
d. velocity
2) Which of the following statements does not describe force?
a. Force causes objects at rest to remain stationary.
b. Force causes objects to start moving.
c. Force causes objects to stop moving.
d. Force causes objects to change direction.
3.) Which of the following is the tendency of an object to maintain its
state of motion?
a. acceleration
c. inertia
b. force
d. velocity
4) Newton’s third law of motion involves the interactions of
a. one object and one force.
c. two object and one force.
b. one object and two forces.
d. two objects and two forces.
5)
A 25 kg mass falling from a cliff on Mars experiences a force of 92.7
N. What is the free fall acceleration at the surface of mars in meters
per second squared?
Answers:
1) C,
2) A,
3) C,
4) D
5) F = MA
A = F/M = 92.7 N/ 25 kg = 3.71 m/s2