Newton laws of motion

What is Newton's First Law of Motion?

An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction, unless acted upon by an unbalanced force.

What is another name for Newton's First Law?

The Law of Inertia.

Define inertia.

Inertia is the tendency of an object to resist changes in its state of motion.

What property of an object is a measure of its inertia?

Mass.

If an object is at rest, what can be said about the forces acting on it?

The net force acting on the object is zero (forces are balanced).

If an object is at rest, what can be said about the forces acting on it?

The net force acting on the object is zero (forces are balanced).

If an object is moving at a constant velocity, what can be said about the forces acting on it?

The net force acting on the object is zero (forces are balanced).

What type of force causes a change in an object's motion?

An unbalanced force.

Give an example of inertia.

When a car suddenly stops, passengers continue to move forward.

What is the SI unit for mass?

Kilograms (kg).

What is Newton's Second Law of Motion?

The acceleration of an object is directly proportional to the net force acting on it, inversely proportional to its mass, and in the direction of the net force.

Write the mathematical formula for Newton's Second Law.

F = ma (Force = mass × acceleration).

What do the symbols stand for in the formula F = ma?

F stands for force, m for mass, and a for acceleration.

What is the SI unit for force?

Newton (N).

How is a Newton defined in terms of other SI units?

1\text{ N} = 1\text{ kg} \cdot \text{m/s}^2 (kilogram-meter per second squared).

What is the SI unit for acceleration?

Meters per second squared (m/s^2).

If you apply a larger net force to an object (keeping mass constant), how does its acceleration change?

Its acceleration increases proportionally.

If you apply the same net force to an object with greater mass, how does its acceleration change?

Its acceleration decreases inversely (it will accelerate less).

Calculate the force required to accelerate a 2 kg object at 3\text{ m/s}^2.

F = ma = (2\text{ kg})(3\text{ m/s}^2) = 6\text{ N}.

An object experiences a net force of 10 N and accelerates at 5\text{ m/s}^2. What is its mass?

m = F/a = 10\text{ N} / 5\text{ m/s}^2 = 2\text{ kg}.

A 5 kg object is pushed with a 20 N force. What is its acceleration?

a = F/m = 20\text{ N} / 5\text{ kg} = 4\text{ m/s}^2.

What is the force of gravity acting on an object near Earth's surface called?

Weight.

What is the formula for weight (W) as a type of force?

W = mg (Weight = mass × acceleration due to gravity).

What is the approximate value of the acceleration due to gravity (g) near Earth's surface?

g \approx 9.8\text{ m/s}^2 (or 9.81\text{ m/s}^2).

Distinguish between mass and weight.

Mass is the amount of matter in an object, a scalar quantity. Weight is the force of gravity acting on an object, a vector quantity.

A person has a mass of 70 kg. What is their weight on Earth?

W = mg = (70\text{ kg})(9.8\text{ m/s}^2) = 686\text{ N}.

What is Newton's Third Law of Motion?

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

What are the two forces in an action-reaction pair called?

Action force and reaction force.

On what objects do action and reaction forces act?

They act on different objects.

Do action and reaction forces cancel each other out? Why or why not?

No, because they act on different objects. For forces to cancel, they must act on the same object.

When you push a wall, what is the reaction force?

The wall pushes back on you with an equal and opposite force.

Describe the action-reaction pair when a rocket is launched.

Action: The rocket expels hot gases downwards. Reaction: The gases exert an equal and opposite upward force on the rocket, propelling it.

Describe the action-reaction pair when a person walks on the ground.

Action: The person pushes backward on the ground. Reaction: The ground pushes forward on the person, propelling them forward.

What is a force?

A push or a pull that can cause an object to accelerate.

Is force a scalar or vector quantity?

A vector quantity (it has both magnitude and direction).

What is friction?

A force that opposes motion between two surfaces in contact.

Give an example of a situation where friction is helpful.

Walking, driving, braking a bicycle.

Give an example of a situation where friction is unhelpful.

Wear and tear on machinery, resistance to movement in engines.

What is the normal force?

The force exerted by a surface perpendicular to the surface of contact, supporting an object.

When an object is at rest on a horizontal surface, what is the action-reaction pair involving the normal force?

Action: The object pushes down on the surface. Reaction: The surface pushes up on the object (normal force).

What is tension?

The pulling force transmitted axially by means of a string, rope, chain, or similar one-dimensional continuous object.

When an object is hanging motionless from a rope, what is the net force on the object?

Zero (the tension force balances the gravitational force).

A book rests on a table. What is the action-reaction pair related to gravity?

Action: Earth pulls the book downwards. Reaction: The book pulls Earth upwards.

If you throw a ball forward, ignoring air resistance, what force causes it to eventually fall?

The force of gravity.

If a car is moving at a constant speed in a straight line, what does Newton's First Law tell us about the forces acting on it?

The net force on the car is zero (the engine's thrust is balanced by friction and air resistance).

Why does it take more effort to push a heavy box than a light box to achieve the same acceleration?

Because a heavy box has more mass, and according to Newton's Second Law (F = ma), more force is needed to accelerate a larger mass.

What happens to an object's motion if the net force acting on it is suddenly removed when it is already moving?

It continues to move at a constant velocity (constant speed and direction) according to Newton's First Law.

Can an object be moving if no forces are acting on it?

Yes, if it was already in motion, it will continue to move at a constant velocity.

If a bird flies in the air, how does Newton's Third Law apply to its wings?

Action: The bird's wings push air downwards and backward. Reaction: The air pushes the bird's wings upwards and forwards, allowing it to fly.

What is the main idea behind Newton's First Law?

Objects tend to maintain their current state of motion (inertia).

What is the main idea behind Newton's Third Law?

Forces always occur in pairs, and these pairs are always equal in magnitude and opposite in direction, acting on different objects.