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I. FORCESI. FORCES
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1. What is a force?1. What is a force?
A lift, push or pull
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2. What is a net force?2. What is a net force?
• The combination of all the forces acting on an object
• Determines whether the velocity of the object will change
• An object accelerates in the direction of the net force
• An object will not accelerate if the net force is zero
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What are the net forces acting on What are the net forces acting on the following?the following?
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3. What are balanced forces?3. What are balanced forces?
• Forces that are equal in size and opposite in direction
• They combine to produce a net force of zero
• No change in motion occurs (no acceleration)
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4. What are unbalanced forces?4. What are unbalanced forces?
• Forces that are unequal
• They cause a change in motion (acceleration)
• Ex: tug of war
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5. How are forces shown?5. How are forces shown?
• Using arrows
• The length of the arrow represents the strength of the force
• The direction of the arrow represents the direction of the force
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Identify whether Identify whether balanced or unbalancedbalanced or unbalanced forces forces are responsible for the following different types of are responsible for the following different types of movement.movement.
• A discus thrown through the air. • A gymnast balanced on a beam.• A sprinter running a bend at a constant speed in
a 200 m race.• A vehicle traveling along a horizontal linear air
track • A car that has a deceleration of 9 m/s2 • A lift traveling downwards at a constant speed of
1m/s.
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6. What is friction?6. What is friction?
• A force between two objects in contact that opposes the motion of the objects
• It will cause a moving object to slow down and eventually stop
• Friction between rough surfaces is greater than friction between smooth surfaces
• Friction is not always bad – some times we need friction (Ex: to walk, to stop a car)
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7. What is air resistance?7. What is air resistance?
• A form of friction caused by air hitting against the surface of a moving object
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8. What is gravity?8. What is gravity?
• The attraction between two particles of matter due to their mass
• Gravity is a force
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9. What is the law of gravitation?9. What is the law of gravitation?
• It states that all objects in the universe attract each other by the force of gravity
• The size of this force of gravity depends on 2 things:
1. The masses of the objects (gravity increases as the masses increases)
2. The distance between the objects (gravity decreases as the distance between the objects increases)
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II. NEWTON’S LAWS OF II. NEWTON’S LAWS OF MOTIONMOTION
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1. Who is Isaac Newton?1. Who is Isaac Newton?
The founder of modern physics
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2. What is Newton’s 12. What is Newton’s 1stst law of law of motion?motion?
• An object at rest remains at rest and an object in motion remains in motion at a constant velocity unless acted upon by an unbalanced force
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3. What are some examples of 3. What are some examples of Newton’s 1Newton’s 1stst law of motion? law of motion?
• Riding in a car and slam on brakes and you continue forward
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4. What is inertia?4. What is inertia?
• The tendency of an object to remain at rest or in motion with a constant velocity
• All objects have inertia because they resist changes in motion
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5. What is Newton’s 25. What is Newton’s 2ndnd law of law of motion?motion?
• An unbalanced force acting on an object equals the object’s mass times its acceleration.
• It describes the effect of unbalanced forces acting on an object
• The greater the force, the greater the acceleration if the mass remains constant
• The greater the mass, the greater the force needed to accelerate an object
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6. What is the formula for Newton’s 6. What is the formula for Newton’s 22ndnd law of motion? law of motion?
Force = mass x acceleration
or
F = ma
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7. What are some examples of 7. What are some examples of Newton’s 2Newton’s 2ndnd law of motion? law of motion?
• Pushing an empty grocery cart vs. pushing a full grocery cart
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8. What unit is used to measure 8. What unit is used to measure force?force?
• Newton
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10. What is weight?10. What is weight?
• A measure of the force of gravity on an object
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11. How can F = ma be used to 11. How can F = ma be used to calculate your weight?calculate your weight?
• Weight = mass x gravitational acceleration
• W = mg
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12. How are weight and mass 12. How are weight and mass different?different?
• Mass is a measure of the amount of matter in an object
• Weight is a measure of the gravitational force an object experiences due to its mass (so weight depends on gravity)
• An object’s weight changes when gravity changes but mass always stays the same.
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14. What is Newton’s 314. What is Newton’s 3rdrd law of law of motion?motion?
• (law of action and reaction) for every action force, there is an equal and opposite reaction force
• Forces always occur in pairs
• The action/reaction forces act on different objects
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15. What are some examples of 15. What are some examples of Newton’s 3Newton’s 3rdrd law of motion? law of motion?
rocketry
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17. What are 3 types of frictional 17. What are 3 types of frictional forces?forces?
• Sliding friction – occurs when a solid surface slides over another solid surface
• Rolling friction – occurs when an object rolls across a solid surface (rolling friction tends to be less than sliding friction)
• Static friction – occurs between the surfaces of two objects that touch but do not move against each other. To move an object, static friction must be overcome.
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18. What is a net force?18. What is a net force?
• The combination of all the forces acting on an object
• If the net force is zero, no change in movement occurs.
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• The correct answer is A. To determine the net force, you must subtract the two forces since they are in opposite directions:
20 N – 20 N = 0 N.