Laws of Force and Motion [8.6C]

Four boxes are sliding with constant speed before each box experiences an unbalanced force of 8 N.

Which box would experience the greatest acceleration when the unbalanced force is applied?

• The box with a mass of 2 kg

• The box with a mass of 4 kg

• The box with a mass of 6 kg

• The box with a mass of 8 kg

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A large rock is motionless on a flat sidewalk. Which statement best explains why the rock remains motionless?

• There are no forces acting on the rock.

• The only force acting on the rock is directed toward the sidewalk.

• The forces acting on the rock are all balanced.

• The sidewalk exerts an unbalanced force on the rock.

Newton’s first law of motion, applied to a book sitting on a table, would explain that the book will not move until which of the following conditions is met?

• Gravity on the book can be reduced to zero

• Unbalanced forces act on the book

• Balanced forces act on the book

• Friction being exerted on the book

According to Newton’s third law of motion, if someone jumps off a skateboard, the skateboard will roll backward because–

• the mass of the skateboard is the same as the mass of the person jumping off.

• for the force that sent the person forward, there is an equal force pushing back on the skateboard.

• the air resistance on the person is great and the friction on the skateboard is small.

• the pull of gravity on the person is the same as on the skateboard, regardless of size.

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A bowling ball is rolled with a certain speed and strikes a bowling pin with a force indicated by the arrow in this illustration. When the bowling ball strikes the bowling pin, the force applied by the pin to the ball -

• depends on the mass of the bowling pin.

• must be zero, since the pin is not moving.

• is equal to the force applied by the ball.

• is equal to the force of gravity on both.

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The masses of four objects are given in this table. If all of the objects have the same acceleration, which will require the greatest force to move?

• Object 1

• Object 2

• Object 3

• Object 4

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A ball thrown into the air starts out with an initial upward velocity, but eventually slows and stops before falling back to the ground. Which of the following contributes the most to the change in motion of the ball?

• The initial force with which the ball is thrown

• The downward force of gravity

• The resistance against the atmosphere

• The increase of inertia

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Safety belts protect people in cars in the event of an accident because, according to Newton’s laws of motion, when an impact causes the car to suddenly change its motion -

• the car now has a greater overall mass - its own mass plus the mass of the object by which it has been struck.

• the speed of the people always increases, since now they have not one but two forces acting on them.

• the speed of the car always increases, giving it greater force since the mass will remain the same.

• the people in the car will continue to move in the same direction and at the same speed as before the impact.

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In which of the following situations would the force shown, acting on a sphere of the given mass, result in the greatest acceleration?

• 
• 
• 
• 

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According to Newton’s first law of motion, an object that is moving will change its motion only if what kind of forces act on it?

• Constant forces

• Unbalanced forces

• Strong forces

• Gravitational forces