Newton's Laws of Motion

What is inertia?

• The resistance of any physical object to a change in its state of motion

• The rate of acceleration due to a force

• The tendency of an object to keep doing what it's doing

• The force of gravity on an object

Answer explanation

Inertia is the tendency of an object to keep doing what it's doing, meaning it resists changes to its state of motion. This aligns with the correct choice, emphasizing that objects maintain their current motion unless acted upon by an external force.

According to Newton's second law, the net force is equal to:

• mass / acceleration

• velocity / time

• mass x acceleration

• mass x velocity

Answer explanation

According to Newton's second law, the net force (F) is defined as the product of mass (m) and acceleration (a), expressed as F = m x a. Therefore, the correct answer is mass x acceleration.

What does Newton's third law state?

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

• The force of gravity is 9.81 m/s^2

• An object at rest stays at rest

• Force equals mass times acceleration

Answer explanation

Newton's third law states that for every action, there is an equal and opposite reaction. This means that forces always occur in pairs, with one force acting in one direction and the other force acting in the opposite direction.

What does 'normal force' refer to?

• The force that is perpendicular to the surface on which an object rests

• The force that keeps an object in motion

• The force that an object exerts on itself

• The force that always acts downward

Answer explanation

The 'normal force' is defined as the force that acts perpendicular to the surface on which an object rests. This force counteracts gravity and supports the weight of the object, making it the correct choice.

What is a free body diagram?

• A sketch of the movement of an object over time

• A diagram showing the gravitational force on an object

• A diagram showing all the forces acting on an object

• A detailed drawing of the shape and dimensions of an object

Answer explanation

A free body diagram illustrates all the forces acting on an object, including gravity, friction, and tension. This helps in analyzing the object's motion and interactions, making the correct choice the one that describes this function.

Which type of force(s) will cause a change in an object's motion?

• gravity

• zero net force

• balanced forces

• unbalanced forces

Answer explanation

Unbalanced forces cause a change in an object's motion by creating a net force that results in acceleration. In contrast, balanced forces and zero net force do not change the motion of an object.

A 20 kg bike accelerates at 10 m/s2.  what was the force

• 25 Newtons

• 20 Newtons

• 200 Newtons

• 10 Newtons

Answer explanation

To find the force, use Newton's second law: F = m * a. Here, m = 20 kg and a = 10 m/s². Thus, F = 20 kg * 10 m/s² = 200 N. The correct answer is 200 Newtons.

8 N to the left , and 4 N to the right. Find the net force. Is this balanced 

• 12 N Right  No

• 4 N Left  No

• 12 N Right  Yes

• 4 N Left  Yes

Answer explanation

The net force is calculated by subtracting the right force from the left force: 8 N left - 4 N right = 4 N left. Since the forces are not equal, this is not balanced. Thus, the correct answer is 4 N Left & No.

What is the net force and the direction of movement?

• 50 Newtons, Left

• 50 Newtons, Right

• 500 Newtons, RIght

• 450 Newtons, LEft

Answer explanation

The net force is 50 Newtons directed to the left, indicating that the object is accelerating in that direction. This choice is correct as it matches the calculated net force and its direction.

__________ is the sum of all forces acting on an object. It is capable of accelerating a mass. 

• velocity

• gravity

• net force

• distance

Answer explanation

The net force is the vector sum of all forces acting on an object. It determines the object's acceleration according to Newton's second law, making 'net force' the correct answer.