•
As stated on physiscsclassroom. com Newton's
second law of montion pertains to the behaviour of
objects for which all existing forces are not
balanced. It states that the acceleration of an
object is dependent upon two variables :
. the net force acting upon the object;
. the mass of the object;
The acceleration of an object depends
directly upon the net force acting upon
the object, and inversely upon the mass
of the object.
As the net force acting upon an object
is increased, the acceleration of the
object is increased, and as the mass of
an object is increased, the acceleration
of the object is decreased.
• It can be expressed with a mathematical
equation:
F= M x A
FORCE= MASS X ACCELERATION
• Aristotle was the first
to look at Newton's
laws. Aristotle's view
were widely
accepted because
they seemed to
follow what
everyone observed
through nature.
• Over a period of 20
years, Galileo
observed the motions
of objects rolling
down various inclines
and attempted to
time these events. He
discovered that the
distance an object
traveled was
proportional to the
square of the time
that it was in motion.
• Newton wanted to know why acceleration occurred.
Newton had to give to science and physics the
concept of a force which was mostly unknown at that
time. He clearly demonstrated that:
• acceleration is caused by an unbalanced force acting
on an object.
• gravity is just a special type of acceleration.
Newton's second law applied to the
game of bowling:
Having different masses of bowling balls will create different
accelerations for each ball going down the lane. The more
acceleration the ball has, the harder the ball will hit the pins.
It all varies on how much force is exerted and how much
mass to acceleration the bowling ball has.
Answers
• 1. The cause of acceleration is Force, Acceleration is
produced through the equation: acceleration = Change in
Velocity/Time interval
• 2. The combination of all the forces that act on an object is
called Net Force.
• 3. If forces of 10N and 20N act on an object, both moving in
the same direction the Net force is 30N
• 4. If a force of 50N is exertedon an object in one
direction, and a force of 30N is exerted in the opposite
direction, Then the resulting net force is 20N
• 5. If a cart is being moved by a net force, and then the
net force is doubled, the acceleration of the cart will
also be doubled.
• 6. If a cart is being moved by a net force, and then a
load is dumped into it and the weight is doubled, The
acceleration changes to be half of what it was. because
the same force cannot push double the weight at the
same acceleration.
• 7. Directly proportional means that as one would inscreease, the other
would increase at the exact same rate, and as one would decrease, the
other would decrease at the exact same rate. such as acceleration to net
force - as the net force is increased, the acceleration will increase.
Inversely proportional refers to two values that would increase or
decrease separately, as one value would increase, the other would
decrease, and as one would decrease, the other would increase. Such as
mass and acceleration - with a constant net force, if you increase the
mass, the acceleration will decrease, and if you decrease the mass, the
acceleration will increase.
• 8. Newton's law states: The acceleration produced by a net force on a
body is directly proportional to the magnitude of the net force, in the
same direction as the net force, and inversely proportional to the mass
of the body. - Acceleration = Net force/ Mass
•
9 . How much force must a 20000-kg rocket develop to accelerate
1m/s2?F=MA F=20000KG X 1M/S2 = 20000N
• 10. How much support force does a table exert on a book that
weights 12N when the book is placed on the table = 0N
• 11
• . there are 100N of tension exerted in the strand
• . in each strand there are 25N of tension.
• 12. Friction is a force that always acts in a direction to oppose
motion. It is due to irregularities in the two surfaces that are in
contact.
• 13.
• Net force= 0N
• Acceleration= 0N
• The pressure is the force per unit. Force is what produces accelaration.
• P=F/A
• 16. The 2-kg rock will fall with the same
acceleration as the 1-kg rock, because they are
both free falling and have the same air
resistance. Newton's second law proves that you
need to consider the mass. For example, 10
times as much force acting on 10 times the as
much mass will produce the same acceleration
as 1/10 the force acting on 1/10 the mass. This
can be seen in the equation, F/M =f/m
• 17. A coin and a feather in a vacuum tube can
fall with the same acceleration because there is
no air resistance. Mass doesn't affect an object
that is falling in a vacuum.
• 18. A coin & a feather fall with different accelerations in the
presence of air. Air resistance decreases the net forces of each
object(not much for the coin, but a lot for the feather). Air
resistance builds up to counteract the feather's weight. When the
air resistance of the feather equals the weight of the feather, the
net force is zero and no further acceleration occurs, the feather's
terminal speed. Air resistance on the coin has less effect and is
very small compared to the weight of the coin. So, the coin would
have to fall for several seconds for air resistance to increase.
Terminal speed takes longer to be reached with the coin so it's
acceleration continues.
• 19. The air resistance that acts on a 100 N bag of nails starts
with an acceleration of zero. This makes the net force 0N because
the gravity force is 100N down. Air force must be 100 N up to
balance it out and create a net force of 0N.
• 20. When terminal speed is reached, the air resistance and the
weight of the falling object balances out.
• 21. All things being equal, a heavier skydiver has a greater
terminal speed than a lighter skydiver because air
resistance is less effective on the heavier skydiver. This
means that the heavier person had a longer time to
accelerate, where the lighter person's air resistance
caused them to reach terminal speed sooner, terminating
their acceleration. For both terminal speeds to be equal,
you could add weights to the lighter skydiver to equal the
weight of the heavier person.
• 22. The net force acting on a 25-N freely falling object is
the weight, 25N. When it encounters 15N air resistance
the net force is 10N. 25N are going down, 15N is the
resistance, 10N is pushing up. When it falls fast enough to
encounter 25N air resistance, the net force is 0N. It will
not have any acceleration and it is at terminal speed.