Newton's Laws and Free Body Diagrams

What is Newton's Second Law

• F = -kx

• F = ma

• F = mg

• F = mad

Block of cheese, B, has a mass of 0.5 kg and the wheel of cheese, W, has a mass of 0.4 kg. What is the tension in rope 1? Assume the acceleration is 0 m/s²

• 4.91 N

• 8.83 N

• 3.92 N

• 0.981 N

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You place 16 N worth of bananas on the scale at the store. The scale drops 4 cm once it stops moving. What is the spring constant of this scale?

• 100 N/cm

• 300 N/m

• 400 N/m

• 400 N/cm

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The combination of all the forces acting on an object is the...

• net force

• action force

• reaction force

• balance force

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When determining the NET force on an object you should (TWO correct answers)

• subtract forces in opposite directions

• add forces in the same direction

• divide by velocity

• multiply by acceleration

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Drag the scenario to the correct Newton's Law.

Groups:

(a) Newton's 1st Law

,

(b) Newton's 2nd Law

,

(c) Newton's 3rd Law

• A ball rolling down hill continues to roll until friction makes it slow to a stop.

• It takes less force to move a ping pong ball than a bowling ball.

• A soccer ball will not move until a player kicks it.

• If air lets out of a balloon quickly, it pushes down and the balloon moves up.

• A fireman turns on his hose and is knocked backwards.

• F = ma

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Consider the four free body diagrams. Free-body diagrams are used to show the magnitude and direction of all forces acting on an object in a given situation. Do any of the free body diagrams indicate motion? If yes, which one(s).

• No. In all four free body diagrams the forces are balanced.

• Yes. In B the book is slowing down because of the friction force opposing motion.

• Yes. In D the two forces are unbalanced. The upward force is greater than the force of gravity so the object moves upward.

• Yes. In B and D. In both cases, forces are unbalanced. In B, there is a net force to the left; in D there is a net force upward.

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Liz puts a 1 kg weight and a 10 kg weight on identical sleds. She then applies a 10N force to each sled. Explain why the smaller weight has a larger acceleration.

• The same amount of force is applied to both sleds.

• The acceleration is directly proportional to the sled.

• It indicates the extent of the unbalanced forces present.

• Acceleration depends indirectly on the mass of the object.

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Urban hits his golf ball but is disappointed when it doesn't follow the course to the left. What does Newton's First Law of Motion say about the travel of an object?

• Every action has an equal and opposite reaction applies.

• Inertia accelerates due to the unbalanced forces present.

• An object at rest will move when external force is applied

• It will travel in a straight path unless changed by an external force.

How does this photograph illustrate Newton's third law of motion?

• The greater the swimmer's acceleration, the more force applied and the lower his mass

• The more force the swimmer applies back on the wall, the faster his movement forward in the water

• In order for the swimmer to move forward in the water there must be an unbalanced force acting on the swimmer

• The force acting forward is greater than the force acting in the opposite direction: the swimmer accelerates

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