Motion Class 9 Science 20 Important Questions with answer

20 important questions with answers on the topic of "Motion" for Class 9 Science:

1. What is motion?

Answer: Motion is the change in the position of an object with respect to its surroundings over time. It can be described in terms of displacement, velocity, and acceleration.

2. Define speed. How is it different from velocity?

Answer: Speed is the rate at which an object covers distance, calculated as distance traveled divided by time taken. Velocity is speed with a specified direction, so it is a vector quantity while speed is a scalar quantity.

3. What is the formula for average speed?

Answer: The formula for average speed is: $\text{Average Speed} = \frac{\text{Total Distance Traveled}}{\text{Total Time Taken}}$

4. Define uniform motion.

Answer: Uniform motion occurs when an object covers equal distances in equal intervals of time. Its speed remains constant, and it does not change direction.

5. What is non-uniform motion?

Answer: Non-uniform motion occurs when an object covers unequal distances in equal intervals of time, meaning its speed changes over time.

6. What is displacement?

Answer: Displacement is the shortest distance from the initial to the final position of an object, and it is a vector quantity that has both magnitude and direction.

7. Explain the difference between distance and displacement.

Answer: Distance is the total path length traveled by an object, irrespective of direction, while displacement is the straight-line distance between the starting and ending points, considering direction.

8. What is acceleration?

Answer: Acceleration is the rate at which an object's velocity changes over time. It is a vector quantity and can be positive (speeding up) or negative (slowing down).

9. What is the formula for acceleration?

Answer: The formula for acceleration is: $\text{Acceleration} = \frac{\text{Change in Velocity}}{\text{Time Taken}}$

10. Define uniform acceleration.

Answer: Uniform acceleration occurs when the rate of change of velocity is constant over time. The object accelerates or decelerates at a constant rate.

11. What is the equation of motion for uniformly accelerated motion?

Answer: The equations of motion are:

1. $v = u + at$
2. $s = ut + \frac{1}{2}at^2$
3. $v^2 = u^2 + 2as$ where $u$ is the initial velocity, $v$ is the final velocity, $a$ is acceleration, $s$ is displacement, and $t$ is time.

12. What is the difference between speed and velocity?

Answer: Speed is a scalar quantity representing how fast an object is moving, while velocity is a vector quantity that includes both the speed of the object and the direction in which it is moving.

13. How do you represent motion graphically?

Answer: Motion can be represented graphically using distance-time graphs and velocity-time graphs. In a distance-time graph, the slope represents speed, while in a velocity-time graph, the slope represents acceleration and the area under the curve represents displacement.

14. What is the significance of the slope in a distance-time graph?

Answer: The slope of a distance-time graph represents the speed of the object. A steeper slope indicates a higher speed, while a flatter slope indicates a lower speed.

15. How is acceleration measured in terms of velocity and time?

Answer: Acceleration is measured as the change in velocity divided by the time taken for that change, represented by the formula: $a = \frac{\Delta v}{\Delta t}$

16. What is free fall?

Answer: Free fall is the motion of an object falling solely under the influence of gravity, without any air resistance. The acceleration due to gravity is constant and is approximately $9.8 \, \text{m/s}^2$ near the Earth's surface.

17. Explain the concept of relative motion.

Answer: Relative motion is the motion of an object as observed from a particular frame of reference. It can differ depending on the observer's own motion or stationary position.

18. What is the difference between average speed and instantaneous speed?

Answer: Average speed is the total distance traveled divided by the total time taken, while instantaneous speed is the speed of an object at a specific moment in time.

19. How does friction affect motion?

Answer: Friction is a force that opposes the relative motion between surfaces in contact. It can slow down or stop motion and affect the acceleration of an object.

20. What is the significance of the area under a velocity-time graph?

Answer: The area under a velocity-time graph represents the displacement of the object. It shows the total distance covered in a given time interval when considering velocity and time.

These questions cover fundamental concepts and provide a comprehensive understanding of the chapter on motion.