Transcript Reviewing Motion & Forces

Reviewing Motion & Forces
1. How do scientists express force?
• Newton (N)
2. What is net force?
• The total combination
of forces on an object.
• Same direction (add)
• Different direction
(subtract)
3. How are balanced and unbalanced
forces different? Give an example for
each.
• Balanced forces mean
net force = zero.
• Unbalanced forces
mean the net force
does NOT equal zero.
4. Name and describe each type of
Kinetic friction.
• Sliding Friction is two
surfaces rubbing back
and forth against each
other. (ice skating)
• Rolling Friction is
anything circular that
rolls over another
surface. (bike)
5. What are some ways of increasing
and decreasing friction?
• Increasing friction can
be done by making the
surface rougher (like
putting sand on an icy
sidewalk)
• Decreasing friction can
be done by using a
lubricant (oil) or making
the surface smooth
(sanding a piece of
wood)
6. What is the difference between
kinetic and static friction?
• Kinetic = motion
• Static = no motion
7. State the law of universal
gravitation. Why is it called universal?
• Gravity increases as
mass increases (more
mass = more gravity).
• Gravity decreases as
distance increases
(more distance = less
gravity).
• It is universal because it
applies to every
situation involving
gravity!
8. How can you illustrate the two parts
of the Law of Gravitation?
• The closer you get to
Earth the more its
gravitational force pulls
you down.
• Jupiter has more mass
than Earth; therefore
Jupiter has a greater
gravitational force.
9. Who was Sir Isaac Newton?
• He was an English
scientist who lived in
the 1600s and studied
physics, mathematics,
and astronomy.
10. If Venus and Earth have the same
mass, why is the gravity between
Venus and the sun greater that the
gravity between Earth and the sun?
• Think about the
Universal Law of
Gravity…
• Which planet is closer
to the sun?
• Venus is closer to the
sun so the sun’s gravity
affects Venus more than
Earth.
11. Explain why weight is expressed in
Newtons (N)?
• Weight is the measure
of gravitational pull.
• Gravity is a force.
• All forces are measured
in Newtons.
12. What is the difference between
weight and mass?
• Weight is the measure
of gravity, unit is
Newtons, use a spring
scale.
• Mass is how much
matter/stuff an object
contains, unit is the
gram, use a triple beam
balance.
13. What does Newton’s first law say?
• An object in motion will
stay in motion, an
object at rest will stay at
rest, until acted on by
an unbalanced force.
14. Newton’s first law is sometimes
known as the Law of
_________________.
•INERTIA
15. What formula goes with Newton’s
2nd law?
•F = m x a
• Force = Mass x Acceleration
• More mass means less
acceleration unless you use
MORE force!
16. If you have a bulldozer and a
Porsche at a stoplight, what would be
the relationship between force, mass,
and acceleration on these two
vehicles?
• The bulldozer has more
mass so it needs more
force to get it going or
to make it stop.
• The Porsche has less
mass so it needs less
force to get greater
acceleration.
17. What does Newton’s third law say?
• For every action there is
an equal and opposite
reaction.
18. This means that all forces act in
_________________.
•PAIRS
19. List 5 action-reaction examples.
•
•
•
•
•
Hitting a baseball.
Swimming
Rocket taking off.
Rabbit hopping.
Cutting with scissors.