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Big Ideas—Newton's Laws
3rd six weeks review handout
Force:
1. Define force.
Force is a push or pull
2. Define net force.
Net force is when two or more forces act ona n object at the same time,
the forces combine.
3. What is the result of unbalanced forces?
The object will move in the direction of the greater force.
4. Which would have more friction, a car traveling down a street or a toy remote-control car
traveling on the same street? Why?
The actual car has more friction because there is more mass, therefore
more mass pressing the surfaces together.
5. Define friction.
Friction is the force that opposes the sliding motion of two surfaces that
are touching each other.
6. What causes friction?
Friction is caused by the microwelds that form where the surfaces are in
contact.
7. Do surfaces touch more when there is less force or greater force?
Greater force
8. Define and give an example of each type of friction:
Definition
Force that keeps two surfaces at rest from sliding
Static
across from each other
Force that works against the motion of two surfaces
Sliding
that are sliding across each other
Force between a rolling object and the surface it rolls
Rolling
on
Opposing force caused by a fluid (liquid/gas)
Fluid
--air resistance, water resistance
Example
Box not moving on the ground
Box sliding across the floor
Tire rolling on the pavement
Swimming in water
Gravity:
9. Define Gravity.
Gravity is an attractive force between any two objects that depends on the
masses of the objects and the distance between them.
10. What two things can cause the gravitational force between objects to increase?
Gravitational force is caused by mass and distance between objects. The
greater the mass or the closer the distance, the greater the gravity between
the two objects.
Newton’s Laws
11. Define the law if inertia.
An object at rest will remain at rest and an object in motion will remain in
motion, unless acted upon by and unbalanced force.
12. What is inertia?
The tendency of an object to resist any change in its motion
13. Compare the inertia of a car to the inertia of a bicycle.
The car will have greater inertia because is has more mass.
14. Define the second law.
F=ma The net force acting on an object causes the object to accelerate in
the direction of the net force.
15. What is the formula for this law?
F=ma, where F is force in Newtons (N), m is mass in kilograms (kg), and
a is acceleration in meters per second per second (m/s/s or m/s2)
16. You apply a force of 2 N to a toy car and to a real car. Which car has the greater acceleration?
Why?
The toy car will have the greater acceleration because it has a small mass.
That means it will require a small force to move it.
17. Define action-reaction law.
For every action, there is an equal and opposite reaction.
18. **When we walk, we are applying a downward force toward the earth, while the earth is
applying and upward force on us. How is it that we are able to move when we know about net
forces?
The forces are acting on objects that have different masses (you and the
earth), so even thought the forces are equal, their net forces are not equal.
Unequal net forces determine the direction you move. You are able to
walk.
Application of Newton’s Laws
19. Using the law of inertia, explain how seatbelts in vehicles work.
When a car collides, it stops instantly but your body want to continue in
motion due to inertia. The seat belt is supposed to lock the instant your car
makes that instant stop and prevent you from continuing forward ( and
injury).
20. Calculate the weight of a 50-kg person on Earth using the formula F=mg. Remember,
g=9.8m/s2.
F=mg
= 50kg * 9.8m/s2
= 490 N
21. Define air resistance.
Force that opposes the movement of object through the air
22. Define terminal velocity.
The highest speed a falling object can reach, depending on its size, shape,
and mass.
23. What is free fall?
When gravity is the only force acting on an object
24. Why do astronauts in the space shuttle weigh less?
The astronauts are in constant freefall. They also experience
weightlessness.
Astronaut Reentry—PBL
25. Give one example of how you used Newton’s laws to design your space capsule.
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26. How did mass effect the result of your capsule’s performance and survival of your egg?
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27. How did you use air resistance in your design? How did it affect the result of your capsule’s
performance and survival of your egg?
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