Forces and Acceleration

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.

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

SI unit of force is

• N

• Kgf

• dyne

• gf

Answer explanation

The SI unit of force is the Newton, abbreviated as N. Other units like kgf (kilogram-force), dyne, and gf (gram-force) are not SI units. Therefore, the correct answer is N.

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

• Frictional force

• Normal force

• Gravitational force

• Tension force

Answer explanation

Gravitational force is a non-contact force that acts at a distance, attracting objects with mass. In contrast, frictional, normal, and tension forces require direct contact between objects.

Tags

NGSS.MS-PS2-4

NGSS.MS-PS2-5

What is the relationship between mass and weight?

• Weight is mass minus acceleration due to gravity

• Weight is mass plus acceleration due to gravity

• Weight is mass multiplied by acceleration due to gravity

• Weight is mass divided by acceleration due to gravity

Answer explanation

Weight is the force exerted by gravity on an object, calculated as the product of its mass and the acceleration due to gravity (W = m * g). Thus, the correct relationship is that weight is mass multiplied by acceleration due to gravity.

What is the effect of increasing the mass of an object on its acceleration, assuming the force applied remains constant?

• Acceleration remains the same

• Acceleration becomes zero

• Acceleration increases

• Acceleration decreases

Answer explanation

According to Newton's second law, F = ma. If the force (F) is constant and the mass (m) increases, the acceleration (a) must decrease, as a = F/m. Therefore, increasing mass results in decreased acceleration.

Tags

NGSS.MS-PS2-2

Which of the following forces is responsible for keeping a satellite in orbit around the Earth?

• Normal force

• Tension force

• Gravitational force

• Frictional force

Answer explanation

The gravitational force is the key force that keeps a satellite in orbit around the Earth. It pulls the satellite towards the Earth, providing the necessary centripetal force for its circular motion.

Tags

NGSS.MS-PS2-4

What is the effect of air resistance on a falling object?

• It has no effect on the object's speed

• It changes the object's mass

• It decreases the object's speed

• It increases the object's speed

Answer explanation

Air resistance opposes the motion of a falling object, leading to a decrease in its speed. As the object falls, the force of air resistance increases until it balances the force of gravity, resulting in terminal velocity.

Tags

NGSS.MS-PS3-1

NGSS.MS-PS3-5

Which of the following describes the motion of an object with balanced forces acting on it?

• The object accelerates

• The object remains at rest or moves with constant velocity

• The object changes direction

• The object gains mass

Answer explanation

When balanced forces act on an object, it does not accelerate. Instead, it either remains at rest or moves with a constant velocity, as per Newton's first law of motion.