Exploring Newton's Laws and Gravity

Which of Newton's Laws states that an object at rest will remain at rest unless acted upon by an external force?

• Newton's First Law

• Newton's Second Law

• Newton's Third Law

• Law of Universal Gravitation

Answer explanation

Newton's First Law states that an object at rest will remain at rest unless acted upon by an external force. This principle highlights the concept of inertia, which is fundamental to understanding motion.

What is the formula for Newton's Second Law of Motion?

Answer explanation

Newton's Second Law of Motion states that the force (F) acting on an object is equal to the mass (m) of the object multiplied by its acceleration (a). Thus, the correct formula is F = ma.

According to Newton's Third Law, what happens when you push against a wall?

• The wall pushes back with an equal and opposite force

• The wall absorbs the force

• The wall moves away

• No force is exerted by the wall

Answer explanation

According to Newton's Third Law, for every action, there is an equal and opposite reaction. When you push against a wall, the wall exerts an equal and opposite force back on you, which is why the correct answer is that the wall pushes back.

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Which constant is used in the Law of Universal Gravitation?

Answer explanation

The Law of Universal Gravitation uses the constant G, known as the gravitational constant, which quantifies the strength of the gravitational force between two masses.

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If a 2 kg object is acted on by a net force of 10 N, what is its acceleration?

Answer explanation

Using Newton's second law, F = ma, we can find acceleration (a) by rearranging the formula to a = F/m. Here, F = 10 N and m = 2 kg, so a = 10 N / 2 kg = 5 m/s². Thus, the correct answer is 5 m/s².

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A planet has twice the mass of Earth but the same radius. How does the gravitational force at its surface compare to Earth's?

• Half as strong

• The same

• Twice as strong

• Four times as strong

Answer explanation

Gravitational force is proportional to mass and inversely proportional to the square of the radius. Since the planet has twice the mass of Earth and the same radius, the gravitational force at its surface is twice as strong.

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Which of the following best describes inertia?

• The tendency of an object to resist a change in motion

• The force that pulls objects toward Earth

• The acceleration of an object due to gravity

• The reaction force to an applied force

Answer explanation

Inertia is defined as the tendency of an object to resist changes in its state of motion. This means that an object at rest will stay at rest, and an object in motion will continue moving at a constant velocity unless acted upon by an external force.

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If the distance between two objects is tripled, how does the gravitational force between them change?

• It becomes 1/3 as strong

• It becomes 1/6 as strong

• It becomes 1/9 as strong

• It becomes 3 times as strong

Answer explanation

According to Newton's law of gravitation, the force is inversely proportional to the square of the distance. If the distance is tripled, the force becomes 1/(3^2) = 1/9 as strong.

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A 5 kg object is moving at a constant velocity. What is the net force acting on it?

• 0 N

• 5 N

• 9.8 N

• 49 N

Answer explanation

Since the object is moving at a constant velocity, according to Newton's first law, the net force acting on it is 0 N. There is no acceleration, so the forces are balanced.

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Which equation represents the Law of Universal Gravitation?

Answer explanation

The Law of Universal Gravitation is represented by the equation F = G\frac{m_1 m_2}{r^2}, which describes the gravitational force between two masses. The other equations pertain to different physical laws.

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