Understanding Gravity and Forces in Physics

This lecture introduces Newton's laws of motion and gravity, explaining forces as vector quantities with magnitude and direction. It covers Newton's first law, emphasizing inertia and the role of external forces like friction. The second law relates force, mass, and acceleration, while the third law discusses action-reaction pairs. The universal law of gravitation is explored, highlighting the weak nature of gravitational forces compared to electromagnetic forces. Examples and calculations illustrate these concepts, emphasizing their universal applicability.

What is a force in physics?

• A vector quantity with only direction

• A scalar quantity with direction

• A vector quantity with magnitude and direction

• A scalar quantity with only magnitude

According to Newton's First Law, what happens to a body at rest or in motion unless acted upon by an external force?

• It accelerates indefinitely

• It remains at rest or in constant motion

• It changes its state randomly

• It stops immediately

What is the difference between mass and weight?

• Mass is the gravitational force on an object, weight is the amount of matter

• Mass and weight are the same

• Mass changes with location, weight remains constant

• Mass is the amount of matter, weight is the gravitational force on an object

What does Newton's Second Law of Motion state?

• Force is equal to mass divided by acceleration

• Force is equal to mass times velocity

• Force is equal to mass times acceleration

• Force is equal to acceleration divided by mass

What unit is used to measure force?

• Meter per second

• Newton

• Kilogram

• Joule

What does Newton's Third Law of Motion imply?

• Objects in motion stay in motion

• Gravitational force is inversely proportional to distance

• Force is proportional to mass

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

In the context of Newton's Third Law, what happens when a swimmer pushes against the wall of a pool?

• The swimmer remains stationary

• The wall does not exert any force

• The swimmer moves backward

• The wall exerts a force equal and opposite to the swimmer's push

What is the gravitational constant (G) used in Newton's Universal Law of Gravitation?

• 6.674 × 10^-11 N m²/kg²

• 9.8 m/s²

• 3.14

• 1.99 × 10^20 N

Why is gravity considered a weak force?

• It only acts on Earth

• It does not affect large objects

• It is easily overcome by other forces

• It only acts over short distances

What is the gravitational force between Earth and the Moon?

• 6.674 × 10^-11 N

• 9.8 N

• 1.99 × 10^20 N

• 1.5 m/s²