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A. Fill in the blanks
- A body moving along a circular path is said to be moving in a circular motion.
- Motion in a straight line is called rectilinear motion.
- The SI unit of distance is metre (m).
- The SI unit of time is second (s).
B. Tick (✓) the correct answer
1. The correct formula is—
✅ speed = distance / time
(✔ Fourth option)
2. The distance covered is—
Using the formula:
Distance=Speed×Time
Given values from the question:
- Speed = 3 km/h
- Time = 12 h
So,
Distance = 3 × 12 = 36 km
✅ Correct answer: 36 km
3. Out of the following distance–time graphs, the graph representing a truck at rest is—
When an object is at rest, distance does not change with time. Therefore, the graph is a horizontal straight line.
✅ Correct answer: A
C. Define the following questions in brief
1. A boy walks to his school with a constant speed of 4 km/h and reaches there in 30 minutes. Find the distance of the school from his house.
Given:
- Speed = 4 km/h
- Time = 30 minutes = 1/2 hour
Using the formula:
Distance=Speed×Time
Distance = 4 × 1/2 = 2 km
✅ Answer: The distance of the school from his house is 2 km.
2. The distance between two stations is 216 km. A bus takes 6 hours to cover this distance. Calculate the average speed of the bus in km/hour.
Given:
- Distance = 216 km
- Time = 6 h
Using the formula:
Speed=TimeDistance
Speed = 216 ÷ 6 = 36 km/h
✅ Answer: The average speed of the bus is 36 km/h.
3. Two cars A and B, starting at the same time, from the same point are moving with average speeds of 40 km/h and 60 km/h respectively. Find how far will Car B be from Car A after 5 hours.
Difference in speed = 60 − 40 = 20 km/h
Time = 5 h
Distance between them after 5 h:
Distance=Relative Speed×Time
Distance = 20 × 5 = 100 km
✅ Answer: Car B will be 100 km ahead of Car A after 5 hours.
4. A car moves at the speed of 40 km/h for 15 minutes and then with a speed of 60 km/h for the next 15 minutes. Find the total distance covered by the car in these 30 minutes.
First 15 minutes = 1/4 hour
Distance covered in first 15 minutes:
40 × 1/4 = 10 km
Distance covered in next 15 minutes:
60 × 1/4 = 15 km
Total distance = 10 + 15 = 25 km
✅ Answer: The total distance covered by the car is 25 km.
5. Define the term ‘Periodic motion’. Give two examples of periodic motions that can be used to measure time.
Periodic motion is the motion which repeats itself after equal intervals of time.
Examples:
- Oscillation of a pendulum
- Rotation of the Earth around its axis
✅ These periodic motions are used to measure time accurately
When a man is standing at one place, the distance does not change with time. Therefore, the graph will be a horizontal straight line parallel to the time axis.
📌 Graph shape: Horizontal line
(b) A man walking on a level, straight and narrow road, with a constant speed.
When a person walks with constant speed, equal distances are covered in equal intervals of time. Therefore, the graph will be a straight sloping line.
📌 Graph shape: Straight upward slanting line
Explanation:
Distance–time graphs help us understand movement visually. A flat line shows stillness and patience, like someone calmly waiting at a bus stop. A steadily rising line represents disciplined and regular movement, just like a person walking with focus toward a destination. These graphs connect science with everyday human experiences and make motion easier to understand.
D. Answer the following questions in brief
1. Distinguish between uniform and non-uniform motion. Give one example of each.
| Uniform Motion | Non-uniform Motion |
|---|---|
| When an object covers equal distances in equal intervals of time, its motion is called uniform motion. | When an object covers unequal distances in equal intervals of time, its motion is called non-uniform motion. |
| The speed of the object remains constant. | The speed of the object keeps changing. |
| Example: A train moving at a constant speed on a straight track. | Example: A car moving in city traffic. |
Explanation:
In our daily life, we rarely move with perfectly uniform speed. Traffic, road conditions, weather, and human reactions continuously affect motion. Uniform motion helps scientists and engineers make accurate calculations, while non-uniform motion reflects the natural movement we observe around us every day.
2. Draw the shape of distance–time graph for:
(a) A man waiting for a bus, standing at one point, on a bus-stand.
When a man is standing at one place, the distance does not change with time. Therefore, the graph will be a horizontal straight line parallel to the time axis.
📌 Graph shape: Horizontal line
(b) A man walking on a level, straight and narrow road, with a constant speed.
When a person walks with constant speed, equal distances are covered in equal intervals of time. Therefore, the graph will be a straight sloping line.
📌 Graph shape: Straight upward slanting line
Explanation:
Distance–time graphs help us understand movement visually. A flat line shows stillness and patience, like someone calmly waiting at a bus stop. A steadily rising line represents disciplined and regular movement, just like a person walking with focus toward a destination. These graphs connect science with everyday human experiences and make motion easier to understand.
E. Answer the following questions
1. A farmer moves along the boundary of a rectangular field ABCD as shown in the figure. He takes 4 minutes to travel around the field.
Given:
- Length of field = 80 m
- Breadth of field = 40 m
To find whether the motion is uniform or non-uniform, first calculate the total distance covered.
Perimeter of rectangle:
Perimeter of Rectangle=2(l+b)
= 2(80 + 40)
= 2 × 120
= 240 m
Time taken = 4 minutes
Average speed:
Average Speed=Total TimeTotal Distance
= 240 ÷ 4
= 60 m/min
Answer:
The farmer’s motion can be considered uniform motion if he moves with the same speed throughout the boundary.
Average speed of the farmer = 60 m/min
Explanation:
A farmer works with discipline and consistency every day. While moving around the field, he carefully observes crops, soil, and boundaries. Science helps us understand such everyday activities mathematically. Motion around the field becomes an excellent real-life example of how distance, time, and speed are connected in practical life.
2. During rainy season, Shivam noticed that the thundering sound was heard 6 seconds after the lightning was seen by him. If speed of sound in air is 340 m/s, find the distance of the point where thunder is produced.
Given:
- Speed of sound = 340 m/s
- Time = 6 s
Using the formula:
Distance=Speed×Time
Distance = 340 × 6
= 2040 m
Answer:
The thunder was produced at a distance of 2040 metres or 2.04 km away.
Explanation:
Lightning is seen before thunder is heard because light travels much faster than sound. During rainy weather, this natural phenomenon reminds us of the amazing powers of nature. Understanding such events through science helps us stay aware and safe during storms and teaches us how scientific knowledge explains daily experiences around us.
3. (a) How can we make a simple pendulum?
A simple pendulum can be made by:
- Tying a small heavy object (called a bob) to one end of a thread.
- The other end of the thread is fixed to a rigid support.
- The bob is displaced slightly and released so that it swings to and fro.
Explanation:
A simple pendulum is one of the easiest scientific models made using ordinary objects around us. It teaches students that science is not limited to laboratories; even simple materials can help us understand important principles of motion and time.
3. (b) A simple pendulum takes 10 seconds to complete 5 oscillations. Find the time period of the pendulum.
Given:
- Total time = 10 s
- Number of oscillations = 5
Using the formula:
Time Period=Number of OscillationsTotal Time
Time period = 10 ÷ 5
= 2 s
Answer:
The time period of the pendulum is 2 seconds.
Explanation:
The regular to-and-fro motion of a pendulum shows the beauty of periodic motion in nature. Pendulums were once used in clocks to measure time accurately. This demonstrates how careful observation of simple motions helped humans develop reliable methods for timekeeping and scientific progress.