With reference to Galileo’s experiments with the inclined plane, consider the following statements: 1. A marble rolling down an inclined plane decreases its velocity. 2. A marble climbing up an inclined plane decreases its velocity. 3. On an ideal frictionless horizontal plane, a marble would travel forever. Which of the statements given above are correct?

Correct Option The correct option is (c). Explanation Galileo Galilei conducted experiments using inclined planes to understand the nature of motion. His observations challenged Aristotelian physics and laid the groundwork for the concept of inertia, which was later formalized as Newton's First Law of Motion. Statement-wise Analysis - Statement 1 is Incorrect. When a marble rolls down an inclined plane, the component of gravitational force acts in the direction of motion. This causes the marble to accelerate, meaning its velocity increases as it descends. - Statement 2 is Correct. When a marble climbs up an inclined plane, it moves against the component of gravitational force. This opposing force causes the marble to decelerate, resulting in a decrease in velocity. - Statement 3 is Correct. On a horizontal plane, gravity acts perpendicular to the direction of motion and does not accelerate or retard the object. Galileo reasoned that in an ideal case where friction is absent, there is no net force to oppose the motion. Consequently, the marble would continue to move with a constant velocity forever. Key Takeaway: An object requires no external force to maintain its motion in a straight line with constant speed if resistive forces like friction are absent. This property is known as inertia.

With reference to Galileo’s experiments… - NCERT Class 9 Science MCQ

NCERT Class 9 Science — Chapter 2: Force and laws of motion

mcqeasy

With reference to Galileo’s experiments with the inclined plane, consider the following statements:

A marble rolling down an inclined plane decreases its velocity.
A marble climbing up an inclined plane decreases its velocity.
On an ideal frictionless horizontal plane, a marble would travel forever.

Which of the statements given above are correct?

NCERT textbook question

From NCERT Science - class 9 · Page 3

Options

A1 and 2 only
B2 only
C2 and 3 only
D1, 2 and 3

Did you get this right?

Solution

Correct Option

The correct option is (c).

Explanation

Galileo Galilei conducted experiments using inclined planes to understand the nature of motion. His observations challenged Aristotelian physics and laid the groundwork for the concept of inertia, which was later formalized as Newton's First Law of Motion.

Statement-wise Analysis

Statement 1 is Incorrect. When a marble rolls down an inclined plane, the component of gravitational force acts in the direction of motion. This causes the marble to accelerate, meaning its velocity increases as it descends.
Statement 2 is Correct. When a marble climbs up an inclined plane, it moves against the component of gravitational force. This opposing force causes the marble to decelerate, resulting in a decrease in velocity.
Statement 3 is Correct. On a horizontal plane, gravity acts perpendicular to the direction of motion and does not accelerate or retard the object. Galileo reasoned that in an ideal case where friction is absent, there is no net force to oppose the motion. Consequently, the marble would continue to move with a constant velocity forever.

Key Takeaway: An object requires no external force to maintain its motion in a straight line with constant speed if resistive forces like friction are absent. This property is known as inertia.

Your note

More from Chapter 2: Force and laws of motion

With reference to the property of inertia, which one of the following comparisons is correct?

easy

The phenomenon of gun recoil is a direct consequence of:

easy

A motor vehicle with a dead battery requires a continuous push to start rather than a sudden jerk. This is best explained by the fact that:

medium

With reference to the motion of a bicycle, consider the following statements: 1. When pedalling stops, the bicycle slows down solely due to the absence of the pedalling force. 2. To keep the bicycle moving at a uniform velocity, the applied force must balance the frictional force. 3. An object moves with a uniform velocity when the pushing force is greater than the frictional force. Which of the statements given above is/are correct?

hard

Consider the following everyday experiences: 1. Dust coming out of a carpet when beaten with a stick. 2. Leaves getting detached from a tree when shaken vigorously is unrelated to the property of inertia. 3. A coin falling into a tumbler when the card below it is flicked. Which of the above can be explained by the Law of Inertia?

medium

Keep practising Chapter 2: Force and laws of motion

Work through every question from this NCERT chapter.

Browse all NCERT Class 9 Science chapters