Forces and Acceleration

What is the unit of force in the International System of Units (SI)?

• Joule

• Newton

• Watt

• Pascal

Answer explanation

The unit of force in the International System of Units (SI) is the Newton. It is defined as the force required to accelerate a one-kilogram mass by one meter per second squared.

Tags

NGSS.MS-PS2-1

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According to Newton's second law of motion, what is the relationship between force, mass, and acceleration?

Answer explanation

According to Newton's second law, force (F) is directly proportional to mass (m) and acceleration (a), expressed as F = m × a. This means that the greater the mass or acceleration, the greater the force required.

Which of the following is an example of a contact force?

• Gravitational force

• Magnetic force

• Frictional force

• Electrostatic force

Answer explanation

Frictional force is a contact force because it arises from the interaction between surfaces in contact. In contrast, gravitational, magnetic, and electrostatic forces act at a distance without direct contact.

What does a free body diagram represent?

• The speed of an object

• The forces acting on an object

• The mass of an object

• The energy of an object

Answer explanation

A free body diagram represents the forces acting on an object, illustrating how these forces interact. It does not depict speed, mass, or energy, making 'the forces acting on an object' the correct choice.

Tags

NGSS.MS-PS2-2

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What is the net force on an object if it is moving with constant velocity?

• Greater than zero

• Less than zero

• Zero

• Equal to the mass of the object

Answer explanation

The net force on an object moving with constant velocity is zero. This is because constant velocity indicates that there is no acceleration, and according to Newton's first law, an object in motion stays in motion unless acted upon by a net force.

Which law of motion states that an object at rest will stay at rest unless acted upon by an external force?

• Newton's first law of motion

• Newton's second law of motion

• Newton's third law of motion

• Law of conservation of energy

Answer explanation

Newton's first law of motion states that an object at rest will remain at rest unless an external force acts on it. This principle highlights the concept of inertia, which is fundamental to understanding motion.

What happens to the acceleration of an object if the net force acting on it is doubled, assuming mass remains constant?

• It is halved

• It remains the same

• It is doubled

• It is quadrupled

Answer explanation

According to Newton's second law, acceleration (a) is directly proportional to net force (F) and inversely proportional to mass (m): a = F/m. If the net force is doubled and mass remains constant, acceleration also doubles.

Tags

NGSS.MS-PS2-2

Which of the following best describes balanced forces?

• Forces that cause an object to accelerate

• Forces that are equal in magnitude and opposite in direction

• Forces that act in the same direction

• Forces that cause an object to change shape

Answer explanation

Balanced forces are defined as forces that are equal in magnitude and opposite in direction, resulting in no net force and no change in motion. This is why the correct choice is 'Forces that are equal in magnitude and opposite in direction'.

What is the effect of friction on the motion of an object?

• It speeds up the object

• It slows down the object

• It has no effect on the object

• It changes the mass of the object

Answer explanation

Friction is a force that opposes the motion of an object. It acts in the opposite direction to the movement, causing the object to slow down. Therefore, the correct answer is that friction slows down the object.

If a diagram shows a force of 10 N to the right and a force of 5 N to the left acting on an object, what is the net force?

• 5 N to the right

• 5 N to the left

• 15 N to the right

• 15 N to the left

Answer explanation

To find the net force, subtract the left force from the right force: 10 N (right) - 5 N (left) = 5 N to the right. Therefore, the net force is 5 N to the right.

Tags

NGSS.MS-PS2-2