Section 1
Section 2
Section 3
Section 4
Other
100
The SI unit of force.
Newton
100
Projectile motion is caused by a. the downward force of gravity. b. an initial forward velocity. c. a final vertical velocity. d. the downward force of gravity and an initial forward velocity.
D
100
How are the size and direction of action-reaction forces are related?
equal in size, opposite in direction
100
Which of the universal forces is the weakest?
gravitational
100
What is Newton's 1st law?
Newton's first law states that an object in motion will remain in motion, and an object at rest will remain at rest, unless a force acts on it.
200
What happens when an unbalanced force acts on an object?
The object accelerates.
200
According to Newton’s second law of motion, the acceleration of an object equals the net force acting on the object divided by the object’s a. mass. b. momentum c. velocity d. weight.
A
200
The product of an object’s mass and velocity is its_________.
Momentum
200
What is the force that keeps an object moving in a circle called?
centripetal force
200
What is Newton's Second Law?
Newton's Second law states that Force = Mass x Acceleration.
300
When a pair of forces are balanced, what is the net force?
Zero
300
Newton’s third law of motion describes a. action and reaction forces. d. centripetal forces. c. balanced forces. d. net force
a
300
Why don’t action-reaction forces cancel each other?
The action force and the reaction force act on different objects. For forces to cancel, they must act on the same object.
300
The observation that a charged object can attract or repel other charged objects led scientists to conclude that there are ____________________ types of charges.
Two
300
What is Newton's 3rd law?
Newton's third law states that for every action, there is an equal and opposite reaction.
400
As you push a cereal box across a tabletop, the sliding friction acting on the cereal box a. acts in the direction of motion. b. equals the weight of the box. c. is usually greater than static friction. d. acts in the direction opposite of motion.
D.
400
The product of an object’s mass and velocity is its a. centripetal force. b. net force. c. momentum. d. weight.
C
400
A 38-kilogram canoe broke free of its dock and is now floating downriver at a speed of 2.2 m/s. What is the canoe’s momentum? Write the formula that you use and show your work.
Formula: Momentum = Mass x Velocity Momentum = 38 kg x 2.2 m/s = 83.6 kg·m/s, downriver
400
The centripetal force acting on the moon continuously changes the ____________________ of the moon’s motion.
Direction
400
A small engine causes a .3-kg model airplane to accelerate at a rate of 11 m/s2. What is the net force on the model airplane? Write the formula that you use and show your work.
Formula: Force = Mass x Acceleration F = .3 kg x 11 m/s2 = 3.3 kg·m/s2 F = 3.3 N
500
A baseball is dropped from 5 feet and another baseball is thrown horizontally from 5 feet. Which ball will hit the ground first? How do you know?
Both balls will reach the ground in the same amount of time. This is because Earth has a 9.8 m/s2 gravitational pull on all objects.
500
The property of matter that resists changes in motion is called a. friction. b. inertia. c. gravity. d. weight.
b
500
What is the direction of the net force on a falling sky diver before she reaches terminal velocity? What is her net force after she is falling at terminal velocity? Explain both of your answers.
Down because the force of gravity is stronger than the force of air resistance; there is no net force on the sky diver because the force of gravity equals the force of air resistance.
500
What force is responsible for the repulsion between two positively-charged particles?
Electric
500
Why does a biker have to pedal harder at a constant speed into the wind on a windy day compared to traveling on the same road at the same speed on a calm day?
On both the calm and windy days, the net force on the biker is zero because the biker is traveling at constant speed. On a calm day, the biker must pedal so that the forward-directed force applied to the bike balances the forces of friction opposing the forward motion. The friction forces primarily take the form rolling friction and fluid friction. On a windy day, the fluid friction force is much greater, so the rider must pedal harder to maintain the same constant speed.
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