III ASSERTION AND REASON:
10. Assertion (A): A clock shows periodic motion.
Reason (R): The hands of a clock move back and forth.
a) Both A and R are true, and R is the correct explanation of A.
b) Both A and R are true, but R is not the correct explanation of A.
c) A is true but R is false.
d) A is false but R is true.
11. Assertion (A): A ceiling fan in motion shows circular motion.
Reason (R): Circular motion occurs when an object moves in a straight line.
a) Both A and R are true, and R is the correct explanation of A.
b) Both A and R are true, but R is not the correct explanation of A.
c) A is true but R is false.
d) A is false but R is true.
IV ANSWER THE FOLLOWING QUESTIONS:
12. Imagine you're an engineer. You must design a robot that can walk straight, turn in a circle, and swing its arms. What types of motion would be involved in each part?
13. Fill in the correct scientific word related to motion and measurement.
(a) I am the SI unit of length. (5 letters)
(b) I swing to and fro. (8 letters)
14. Can an object be in motion with respect to one thing and at rest with respect to another? Explain with an example.
CASE STUDY:
Ravi and his family went on a road trip from Chennai to Bangalore, covering a distance of 350 kilometers. They started at 6:00 AM and reached by 12:00 PM, with two breaks of 30 minutes each for breakfast and fuel. Ravi was curious about the trip and noted the time, speed, and motion of different vehicles they saw on the highway. He saw trucks moving slowly, cars at high speeds, and also bicycles in nearby towns. He also noticed how the wheels of the car moved in circular motion, while the car itself moved in rectilinear motion along the highway.
15. What type of motion was shown by the car moving along the straight highway?
a) Circular motion
b) Rectilinear motion
c) Oscillatory motion
d) Random motion
16. How long did Ravi's journey take, excluding the breaks?
a) 6 hours
b) 5 hours
c) 5.5 hours
d) 6.5 hours
17. Which of the following objects showed circular motion in the case?
a) The steering wheel
b) The entire car
c) Trees by the road
d) Speedometer needle
18. Calculate the average speed of the car during the journey (excluding break time).
Hint: Speed = Distance / Time
Answer (2)
The answers include identifying types of motion and calculating average speed. The journey took 5 hours excluding breaks, and the average speed was 70 km/h. The car exhibited rectilinear motion while the steering wheel showed circular motion.
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III. ASSERTION AND REASON:
Assertion (A): A clock shows periodic motion. Reason (R): The hands of a clock move back and forth.
The correct option is c) A is true but R is false . A clock shows periodic motion because the hands of a clock move in a consistent, repeated pattern (circular motion), which is not back and forth motion.
Assertion (A): A ceiling fan in motion shows circular motion. Reason (R): Circular motion occurs when an object moves in a straight line.
The correct option is c) A is true but R is false . A ceiling fan does show circular motion because its blades rotate around a central point. However, circular motion does not occur when an object moves in a straight line; it occurs when an object moves along a circular path.
IV. ANSWER THE FOLLOWING QUESTIONS:
Imagine you're an engineer. You must design a robot that can walk straight, turn in a circle, and swing its arms. What types of motion would be involved in each part?
Walking straight involves rectilinear motion, where the robot moves along a straight path.
Turning in a circle involves circular motion, where the robot pivots or moves around a central point.
Swinging its arms involves oscillatory motion, a back-and-forth movement typical of a pendulum.
Fill in the correct scientific word related to motion and measurement.
(a) I am the SI unit of length.
The answer is "meter."
(b) I swing to and fro.
The answer is "pendulum."
Can an object be in motion with respect to one thing and at rest with respect to another? Explain with an example.
Yes, an object can be in motion with respect to one reference point and at rest with another. For example, consider someone sitting in a moving bus. The person is at rest relative to other passengers but is moving relative to trees outside the bus.
CASE STUDY:
What type of motion was shown by the car moving along the straight highway?
The correct option is b) Rectilinear motion . The car moves in a straight line along the highway, which is rectilinear motion.
How long did Ravi's journey take, excluding the breaks?
The correct option is b) 5 hours . Ravi started at 6:00 AM and reached at 12:00 PM. The total time was 6 hours, but excluding the two breaks of 30 minutes each, the journey was 5 hours.
Which of the following objects showed circular motion in the case?
The correct option is a) The steering wheel . The steering wheel moves in a circular motion as it's used to steer the car.
Calculate the average speed of the car during the journey (excluding break time). Hint: Speed = Distance / Time
The total distance covered is 350 kilometers and the travel time, excluding breaks, is 5 hours.
Average speed = Time Distance = 5 hour 350 km = 70 km/hour
Therefore, the average speed of Ravi's journey was 70 km/h.
