Unit 2 Section 2: Newton's Laws of Motion Practice Scrimmage

Which of the following best describes inertia?

• The tendency of an object to change its state of motion

• The tendency of an object to resist changes in its state of motion

• The force required to move an object

• The acceleration of an object due to gravity

Answer explanation

Inertia is defined as the tendency of an object to resist changes in its state of motion. This means that an object at rest stays at rest, and an object in motion continues in motion unless acted upon by an external force.

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DOK Level 1: Recall

A car is moving at a constant velocity of 60 km/h. What is the net force acting on the car?

• 0 N

• 60 N

• 600 N

• 6000 N

Answer explanation

The car is moving at a constant velocity, meaning there is no acceleration. According to Newton's first law, if an object is at rest or moving at a constant velocity, the net force acting on it is 0 N.

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DOK Level 1: Recall

Which of the following is a correct representation of Newton's Second Law of Motion?

Answer explanation

Newton's Second Law of Motion states that the force (F) acting on an object is equal to the mass (m) of the object multiplied by its acceleration (a), represented as F = ma. This makes the first choice the correct representation.

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DOK Level 1: Recall

• 5 N

• 10 N

• 15 N

• 20 N

Answer explanation

To find the net force, use Newton's second law: F = m * a. Here, m = 5 kg and a = 2 m/s². Thus, F = 5 kg * 2 m/s² = 10 N. Therefore, the net force acting on the object is 10 N.

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DOK Level 2: Skill/Concept

Which of the following forces acts perpendicular to the surface of contact?

• Frictional force

• Gravitational force

• Normal reaction force

• Tension force

Answer explanation

The normal reaction force acts perpendicular to the surface of contact, supporting the weight of an object. In contrast, frictional force acts parallel to the surface, while gravitational and tension forces do not specifically act perpendicular.

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DOK Level 1: Recall

If an object is in free fall, which of the following forces is acting on it?

• Friction

• Air drag

• Weight (force of gravity)

• Normal force

Answer explanation

In free fall, the only force acting on an object is its weight, which is the force of gravity. Friction, air drag, and normal force are not present in free fall.

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DOK Level 1: Recall

A 10 kg object is at rest on a horizontal surface. What is the normal force acting on the object?

• 0 N

• 10 N

• 98 N

• 100 N

Answer explanation

The normal force equals the weight of the object when at rest. Weight is calculated as mass (10 kg) times gravity (9.8 m/s²), resulting in 98 N. Therefore, the normal force acting on the object is 98 N.

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DOK Level 2: Skill/Concept

Which of the following statements is true according to Newton's Third Law of Motion?

• For every action, there is an equal and opposite reaction.

• An object in motion stays in motion unless acted upon by an external force.

• The acceleration of an object is directly proportional to the net force acting on it.

• The force of gravity acts between all objects in the universe.

Answer explanation

According to Newton's Third Law of Motion, the correct statement is 'For every action, there is an equal and opposite reaction.' This law emphasizes the mutual forces between two interacting objects.

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DOK Level 1: Recall

A 15 kg object is subjected to a net force of 45 N. What is the acceleration of the object?

Answer explanation

To find the acceleration, use Newton's second law: F = ma. Rearranging gives a = F/m. Here, a = 45 N / 15 kg = 3 m/s². Thus, the correct answer is 3 m/s².

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DOK Level 2: Skill/Concept

Which of the following best describes friction?

• A force that acts in the direction of motion

• A force that opposes the relative motion between two surfaces

• A force that acts perpendicular to the surface

• A force that increases the speed of an object

Answer explanation

Friction is defined as a force that opposes the relative motion between two surfaces. It acts in the opposite direction to the movement, making the correct choice 'A force that opposes the relative motion between two surfaces'.

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DOK Level 1: Recall