Science 8: Newton's First Law of Motion

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Questions and Answers

What is the SI unit for weight?

Newton (correct)

Gram

Kilogram

Pound

If the mass of an object is tripled, how does its weight change on Earth?

It is halved.

It is reduced by a third.

It remains the same.

It is tripled. (correct)

What happens to the mass of an object if it is taken to the Moon?

It increases.

It decreases.

It becomes negligible.

It remains constant. (correct)

Calculate the weight of a 1 kg mass on Earth. (Use g = 9.8 m/s²)

9.8 N Signup and view all the answers

What is the weight of a 50 kg person on the Moon?

81.67 N Signup and view all the answers

How does the weight of an object change if the gravitational pull is reduced to 1/6th of that on Earth?

The weight is one-sixth of the original. Signup and view all the answers

What is the gravitational acceleration on the Moon if it is 1/6th of Earth's?

1.63 m/s² Signup and view all the answers

What would be the weight of a 2.2 kg book on Earth?

21.56 N Signup and view all the answers

What is the primary concept illustrated by Newton's First Law of Motion?

An object will not change its state of motion without an external force. Signup and view all the answers

How does friction affect the motion of a sliding object according to Newton's First Law?

Friction acts as an unbalanced force that opposes motion. Signup and view all the answers

Which scenario best illustrates the concept of inertia?

A book resting on a shelf remains stationary. Signup and view all the answers

What is mass in the context of Newton's First Law?

The amount of matter in an object related to its inertia. Signup and view all the answers

Why do moving objects not change their direction according to Newton's First Law?

An external force is required to change their motion. Signup and view all the answers

Which statement best describes acceleration in relation to Newton's First Law?

Acceleration is the result of an unbalanced force acting on an object. Signup and view all the answers

What does the law of inertia explain about an object at rest?

It will stay at rest unless an external unbalanced force acts on it. Signup and view all the answers

In what situation would an object maintain its state of motion indefinitely?

In space, where there is negligible resistance. Signup and view all the answers

What does Newton's first law of motion primarily describe?

The inertia of objects at rest or in motion. Signup and view all the answers

How is weight calculated?

Weight is mass multiplied by acceleration due to gravity. Signup and view all the answers

If an object has a mass of 1 kg and is subject to a net force of 2 Newtons, what is its acceleration?

2 m/s² Signup and view all the answers

In the context of Newton's Second Law, how does increased mass affect acceleration given a constant force?

Increased mass results in decreased acceleration. Signup and view all the answers

What does Newton's Second Law state about an object's motion?

It will change due to an applied net force. Signup and view all the answers

In a scenario where a ball rolls down a hill, what type of acceleration is occurring?

Acceleration because gravity acts in the direction of motion. Signup and view all the answers

If a stationary object receives an unbalanced force, what will happen to the object?

It will begin to move and change its motion. Signup and view all the answers

What effect does the force have when it acts on larger mass objects compared to smaller mass objects?

Larger mass objects require more force to accelerate. Signup and view all the answers

Study Notes

Newton’s First Law of Motion

States that an object at rest remains at rest and an object in motion stays in motion unless acted upon by an external force.
Known as the Law of Inertia, indicating an object's resistance to changes in its state of motion.
Predictable behavior of objects: a stationary ball doesn't roll off a table without an external force.
Movement and direction change only when a force affects the object.
Friction acts as an opposing force causing a sliding object to stop.
In the absence of resistance (like in space), objects can move indefinitely.

Inertia

Defined as the property of objects that opposes changes in motion.
Objects do not accelerate without an external net force.
Acceleration refers to the rate of change of velocity over time; velocity measures position change over time.

Mass and Weight

Mass: the amount of matter in an object (measured in kilograms, kg).
Weight: the gravitational force experienced by an object (measured in newtons, N).
Weight can be calculated using the equation: weight (w) = mass (m) × acceleration due to gravity (g).

Relationship Between Mass and Weight

On Earth, mass and weight are directly proportional; doubling mass doubles weight.
Mass remains constant regardless of location, while weight varies with gravitational pull.
Example calculation:
- Earth: For a 50 kg mass (gravity = 9.8 m/s²), weight = 50 kg × 9.8 m/s² = 490 N.
- Moon: For the same mass (gravity = 1.63 m/s²), weight = 50 kg × 1.63 m/s² = 81.67 N.

Summary of Newton's First Law

States that external forces are required to change an object’s state of rest or constant motion.
Mass is a measure of inertia; greater mass indicates greater resistance to changes in motion.
Weight is a product of mass and gravitational acceleration.

Newton's Second Law of Motion

Describes how force influences acceleration in an object.
The law can be expressed as: force (F) = mass (m) × acceleration (a).
More force is needed to accelerate heavier objects compared to lighter ones.
Deceleration occurs when the applied force is opposite the direction of motion, resulting in negative acceleration.

Applications of Newton's Second Law

Example calculation for force:
- For a 1 kg object with an acceleration of 5 m/s², net force needed = 1 kg × 5 m/s² = 5 N.
For a given net force of 2 N acting on a 1 kg mass, acceleration can be determined as:
- a = ∑F / m = 2 N / 1 kg = 2 m/s², with the direction of acceleration being the same as the net force applied.

Conclusion

Motion changes due to applied forces, highlighting the relationship between force, mass, and acceleration as outlined in Newton’s laws of motion.

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Description

Explore the fundamentals of Newton's First Law of Motion in this quiz designed for 8th-grade science students. Test your understanding of inertia, mass, and how objects respond to forces. Get ready to demonstrate your knowledge and differentiate between concepts!