Newton's Laws of Motion Quiz

Newton's Law of Motion

• An object at rest will remain at rest unless acted on by a net force.
• Forces are considered balanced when they cancel each other out, resulting in a net force of zero.
• An object in motion will continue in motion at a constant velocity unless acted on by a net force.
• Friction opposes motion, and the amount of friction determines how long an object in motion will continue moving.
• In outer space, there's virtually no friction, allowing objects to continue moving at a constant velocity for extended periods.

Newton's First Law of Motion: Inertia

• An object at rest will stay at rest, and an object in motion will stay in motion at a constant velocity unless acted on by a net force.
• This is the "law of inertia," meaning an object wants to maintain its current state of motion.
• It takes force to start an object moving or to change its direction or speed.

Newton's Second Law of Motion: Force and Acceleration

• The net force acting on an object is directly proportional to the mass of the object and the acceleration it experiences. This is expressed as: F = ma (Force = mass x acceleration).
• If the net force acting on an object is zero, then the object's velocity will remain constant (including being at rest).
• If the net force is not zero, then the object will accelerate, meaning its velocity will change.
• If you double the mass of an object and keep the net force constant, the acceleration will be halved.
• If you double the net force acting on an object and keep the mass constant, the acceleration will double.

Momentum & Impulse

• Momentum (p) is a measure of an object's mass in motion and is calculated as p = mv (momentum = mass x velocity).
• A heavier object moving at the same speed as a lighter object will have more momentum.
• The change in momentum is called impulse, calculated as impulse = Δp = FΔt (impulse = change in momentum = force x change in time).
• Another way to express Newton's Second Law is F = Δp/Δt (force = change in momentum over change in time).

Newton's Third Law of Motion: Action and Reaction

• For every action force, there is an equal and opposite reaction force.
• These forces always act on different objects.
• This means that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force back on the first object.
• This can be expressed as: F (action) = -F (reaction).
• The forces are equal in magnitude but opposite in direction.
• The lighter object will experience a higher acceleration than the heavier object when subjected to the same force.

Examples of Newton's Laws in Action

• Throwing a ball: When throwing a ball, you exert a force on it, causing acceleration. The ball exerts an equal and opposite force back on you, causing a slight backward movement.
• Jumping in the air: When jumping, you push down on the ground. The ground pushes back on your feet with an equal and opposite force, propelling you upward.
• A rocket launching: The rocket expels hot gas downward, creating a force that pushes the rocket upward.
• An astronaut in space: To move in space, astronauts need to throw an object (like a ball or tool), creating an opposite force that pushes them in the desired direction.
• A car moving at constant velocity: The forces on a car moving at constant velocity are balanced. The engine's propelling force is equal and opposite to friction and air resistance.