All questions of Motion and Measurement of Distances for Class 6 Exam

One kilometre is equal to 1000 meter.

To convert centimetres to millimetres, multiply by 10. Therefore, a book that is 24 cm long is 240 millimetres long (24 × 10 = 240).

Circular motion is the movement of an object along a circular path. In this type of motion, the object continuously changes its direction while maintaining a constant speed. The correct answer to the question is option 'B' - the direction of motion changes continuously. Let's understand why this is the correct answer in detail.

Direction of Motion
In circular motion, the object moves around a center point in a circular path. As it moves, the direction of the object constantly changes. At any given point on the circular path, the object is moving tangentially to that point. This means that the object is moving perpendicular to the radius of the circle at that point. Therefore, the direction of motion is not fixed but changes continuously.

Velocity
Velocity is a vector quantity that includes both magnitude (speed) and direction. In circular motion, the object maintains a constant speed as it moves around the circle. However, the direction of motion changes continuously, which means the velocity of the object also changes. Therefore, the velocity is not constant in circular motion.

Acceleration
Acceleration is the rate of change of velocity. In circular motion, even though the speed of the object remains constant, its direction changes continuously. This change in direction indicates a change in velocity. As a result, there is a non-zero acceleration in circular motion. The object is constantly accelerating towards the center of the circle, which is called centripetal acceleration.

Centripetal Force
The centripetal acceleration in circular motion is caused by a force called the centripetal force. This force acts towards the center of the circle, pulling the object inward. It is responsible for keeping the object in its circular path. Without this force, the object would move in a straight line tangent to the circle. The centripetal force is required to constantly change the object's direction of motion, thereby causing the continuous change in direction.

In conclusion, in circular motion, the direction of motion changes continuously, the velocity is not constant, and there is a non-zero acceleration. Therefore, the correct answer is option 'B'.

Understanding Periodic Motion
Periodic motion is defined as motion that repeats itself at regular intervals of time. This concept can be observed in various daily activities, one of which is the movement of fan blades.
Why Fan Blades Exhibit Periodic Motion
- Repetitive Movement:
The blades of a fan rotate around a fixed axis, completing a full revolution in a consistent timeframe. This consistent repetition characterizes periodic motion.
- Time Interval:
Each complete cycle of the fan blades returning to their original position occurs within a specific time interval, such as every second or two seconds, depending on the fan's speed.
- Predictable Pattern:
The motion can be predicted, as the blades will always return to the same position after a set duration. This predictability is a hallmark of periodic motion.
Comparing Other Types of Motion
- Non-Periodic Motion:
Unlike periodic motion, non-periodic motion does not follow a consistent pattern or interval. An example would be a person walking randomly in a park.
- Rectilinear Motion:
This type of motion involves movement in a straight line. Fan blades do not move in a straight line; they rotate in a circular path.
- Conclusion:
Since the movement of fan blades is consistent, repetitive, and predictable, it is classified as periodic motion.
Final Thoughts
In summary, the movement of fan blades is categorized as periodic motion because they rotate in a consistent manner, completing cycles at regular intervals. This understanding helps in recognizing how various objects move in our daily lives!

Introduction to Gas Turbine Engines
Gas turbine engines are powerful machines that convert fuel into mechanical energy through combustion. These engines are known for their efficiency and high power-to-weight ratio, making them ideal for certain types of transport.
Transport Modes Using Gas Turbine Engines
- Airplane: The primary mode of transport that uses a gas turbine engine is the airplane.
- How It Works: In an airplane, the gas turbine engine, often referred to as a jet engine, works by drawing in air, compressing it, mixing it with fuel, and igniting the mixture. The high-speed exhaust gases then propel the aircraft forward.
- Advantages: Jet engines provide excellent thrust, enabling airplanes to achieve high speeds and altitudes. They are essential for commercial and military aviation.
Other Modes of Transport
- Train: Most trains operate using diesel engines or electric motors. However, some high-speed trains may utilize gas turbines, but these are less common.
- Ship: While many ships use diesel engines, some modern vessels, like naval ships, may use gas turbines for their propulsion systems. Yet, this is not the standard for all ships.
- Bicycle: Bicycles are human-powered vehicles and do not use engines at all, let alone gas turbine engines.
Conclusion
In summary, the most prominent mode of transport that utilizes gas turbine engines is the airplane. This technology plays a crucial role in enabling efficient and rapid air travel, distinguishing it from other transport methods.

Similarities and Differences in Motion
When comparing the motion of a bicycle and a ceiling fan, it's important to understand how each operates in terms of movement.
Similarities
- Circular Motion:
- Both the bicycle and the ceiling fan exhibit circular motion at different points.
- While the fan blades rotate in a circular path, the bicycle can also move in a circular path when making turns or riding in a circle.
Differences
- Path of Motion:
- A bicycle primarily moves in a straight line when traveling from one point to another. However, it can also move in circles when the rider intentionally steers it that way.
- A ceiling fan, on the other hand, consistently rotates around a central axis, creating a circular motion at all times.
- Type of Motion:
- The bicycle's motion is not exclusively circular; it can be rectilinear (straight line) when moving directly forward or backward.
- The ceiling fan maintains a circular motion, as its blades spin around without deviating from that path.
Conclusion
The correct answer is option 'C' because both the bicycle and the ceiling fan can have circular motion; however, the bicycle's primary movement is often rectilinear unless it is maneuvering in a circular path. This contrast highlights the distinct nature of their movements while acknowledging that both can indeed exhibit circular motion under specific conditions.

To convert metres to centimetres, multiply by 100. Thus, 3.75 metres equals 375 centimetres (3.75 × 100 = 375).

The motion of a leaf falling from a tree is random because it does not follow a predictable or repetitive pattern. It is influenced by factors like wind and air resistance.

Pound is not a unit of length; it is a unit of weight. Inch, yard, and foot are all units used to measure length.