HOTS Questions: Motion and Measurement of Distances | Class 6: Additional Practice PDF Download

Q1: You are given a cotton thread and a wool thread. Which thread can be used to measure the length of an object and why?
Ans: To measure the length of an object, it is preferable to use a thread that does not stretch or expand significantly when tension is applied to it. Comparing cotton and wool threads, the cotton thread would be a better choice for measuring length accurately. This is because cotton fibers are less elastic and have a tendency to stretch less when pulled. Wool, on the other hand, is known to have some elasticity due to its coiled and spring-like structure, which can lead to inaccuracies in measurement. Using a non-stretchable material like cotton ensures that the length measured using the thread closely corresponds to the actual length of the object being measured. This characteristic of cotton makes it more suitable for tasks that demand precision in measurements, such as when using a thread to measure length.

Q2: When a fan is rotating, we observe the blades rotating in opposite directions. Why?
Ans: The phenomenon where the rotating fan blades appear to be moving in opposite directions is due to our eyes' persistence of vision. Our eyes retain an image for a short time even after the actual object has moved. The fan blades are rotating quickly, and since our eyes cannot perceive their individual positions separately, they appear as a continuous blur. This blurring effect, combined with the quick rotation, gives the illusion that the fan blades are moving in opposite directions.

Q3: Name some objects having periodic motion.
Ans: Objects that exhibit periodic motion repeat the same motion at regular intervals. Here are a few examples:

• Pendulum: A swinging pendulum back and forth.
• Earth's Rotation: The Earth rotating on its axis, causing day and night.
• Heartbeat: The rhythmic contraction and relaxation of the heart.
• Tides: The rising and falling of ocean tides.
• Tuning Fork: Vibrations of a struck tuning fork.
• Swing: A swing moving back and forth.

Q4: You have seen your father playing the violin. While playing it, you observed that the strings are creating the sound. Can you tell due to what motion it is giving the sound?
Ans: The sound produced by the strings of the violin is a result of their vibrating motion. When your father plays the violin, he uses a bow to move back and forth across the strings. This action causes the strings to vibrate rapidly. These vibrations create sound waves in the surrounding air, which we hear as musical notes. The motion of the strings, which involves rapid oscillation or vibration, is what gives rise to the sound produced by the violin.

Q5: While playing with a kite, you observe that the kite's motion will not be in the same direction. Why?
Ans: The motion of a kite is influenced by the balance of forces acting on it. The shape of the kite and the angle at which it is held in the wind create a force called "lift" that keeps the kite airborne. Depending on the angle and the strength of the wind, the kite may experience more lift on one side, causing it to deviate from a straight path. This is why the kite's motion may not always align with the direction of the wind.

Q6: What is motion? Explain with an example.
Ans: Motion is the change in position of an object with respect to time. When an object changes its position over time, it is said to be in motion. For example, when a bicycle moves from one place to another, it is undergoing motion.

Q7: Differentiate between distance and displacement.
Ans: Distance is the total path covered by an object during its motion. It is a scalar quantity and is always positive. Displacement, on the other hand, is the shortest distance between the initial and final positions of an object, considering direction. It is a vector quantity and can be positive, negative, or zero.

Q8: Explain the difference between uniform and non-uniform motion with examples.
Ans: Uniform motion is when an object covers equal distances in equal intervals of time. For example, a car moving at a constant speed on a straight road. Non-uniform motion is when an object covers unequal distances in equal intervals of time. For instance, a bicycle moving through a crowded market where its speed keeps changing due to various obstacles.

Q9: How can you measure the length of a curved line using a ruler?
Ans: To measure the length of a curved line using a ruler, follow these steps:

• Place the ruler along the curved line.
• Make sure the ruler's zero mark aligns with the starting point of the curve.
• Follow the curve along the ruler's markings and note where the curve ends.
• The distance from the starting point to the ending point on the ruler gives an approximate measurement of the curved line's length.

Q10: What are the units used to measure distance and speed in the metric system?
Ans: In the metric system:

• Distance is measured in meters (m).
• Speed is measured in meters per second (m/s).
• For example, if a car travels 100 meters in 20 seconds, its speed is calculated as 100 m / 20 s = 5 m/s.