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All questions of Measuring motion for Class 8 Exam

Study the given Venn diagram, Which of the motions described by different bodies are most likely to be I, II and III?
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'C'. Can you explain this answer?

Amit Sharma answered
Option 1,2 and 3 are rotatory motion. Rotatory motion, also referred to as rotational motion or circular motion, is physical motion that happens when an object rotates or spins on an axis. 

If a distance-time graph is a straight line sloping downwards from left to right, the object is:
  • a)
    Moving towards the origin
  • b)
    Moving away from the origin
  • c)
    Accelerating
  • d)
    Decelerating
Correct answer is option 'B'. Can you explain this answer?

Focus Academy answered
A straight line sloping downwards from left to right on a distance-time graph indicates that the object is moving away from the origin (assuming the origin represents the starting point). This could represent a scenario where the object is moving in the opposite direction of the origin with a constant speed (if the line is straight) or decreasing speed (if it curves downwards gradually).

In circular motion, the
  • a)
    Direction of motion is fixed
  • b)
    Direction of motion changes continuously
  • c)
    Acceleration is zero
  • d)
    Velocity is constant.
Correct answer is option 'B'. Can you explain this answer?

Muskaan Joshi answered
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'.

Given figure shows a measuring cylinder (incm3) before and after the immersion of an irregular solid object. The volume of the object is 
  • a)
    82 cm3
  • b)
    12 cm3
  • c)
    30 cm3
  • d)
    18 cm3​
Correct answer is option 'B'. Can you explain this answer?

Shounak Joshi answered
Initial volume of water in the cylinder, (before the immersion of the object) 
V= 70cm3
Final volume in the cylinder (after the immersion of the object) 
V= 82cm3
Hence, volume of the object immersed in the cylinder = Final volume - Initial volume 
= 82 cm3−70 cm
= 12 cm3

Give two examples of periodic motion.
  • a)
    A child on a swing and a car moving on a road
  • b)
    A pendulum in a clock and the orbit of the Earth around the Sun
  • c)
    A spinning top and a bird flying in the sky
  • d)
    A leaf falling from a tree and a river flowing
Correct answer is option 'B'. Can you explain this answer?

Get Idea answered
Periodic motion refers to movements that repeat at regular intervals. Examples include a pendulum in a clock, which swings back and forth in a regular pattern, and the orbit of the Earth around the Sun, which follows a consistent cycle. Both exhibit repetitive and predictable motion

What do we use to measure curved lengths?
  • a)
    Thread
  • b)
    Wood
  • c)
    Sand
  • d)
    Paper
Correct answer is option 'A'. Can you explain this answer?

Get Idea answered
Measuring Curved Lengths


  • Thread: Threads are commonly used to measure curved lengths. You can wrap a thread around the curve and then measure the length of the thread to determine the curved length accurately.

  • Wood: While wood can be used for measuring straight lengths, it is not an ideal tool for measuring curved lengths as it cannot conform to the shape of the curve.

  • Sand: Sand is not a practical tool for measuring curved lengths as it would not provide an accurate measurement and would be messy to work with.

  • Paper: Paper is also not suitable for measuring curved lengths as it is a flat and rigid material that cannot adapt to the shape of the curve.


Therefore, the most appropriate tool for measuring curved lengths is a thread due to its flexibility and ability to conform to the shape of the curve.

In which year, SI system was recommended by general conference of weights and measures?
  • a)
    1950
  • b)
    1971
  • c)
    1960
  • d)
    1980
Correct answer is option 'B'. Can you explain this answer?

Get Idea answered
Year of Recommendation for SI System


  • General Conference of Weights and Measures: The SI system was recommended by the General Conference of Weights and Measures in 1971.

  • Significance: This recommendation marked a significant milestone in the standardization of units of measurement worldwide.

  • Implementation: The SI system, also known as the International System of Units, is now widely used in scientific, engineering, and everyday applications.

  • Consistency: The adoption of the SI system has helped to promote consistency and accuracy in measurements across different fields and industries.

  • Updates: The SI system continues to be updated and refined to ensure its relevance and effectiveness in modern measurement practices.

5 kilometres are equal to
  • a)
    5,00,000 metre
  • b)
    50,000 metre
  • c)
    5000 metre
  • d)
    500 metre
Correct answer is option 'C'. Can you explain this answer?

Get Idea answered
Conversion of Kilometres to Metres:


  • 1 kilometre = 1000 metres

  • 5 kilometres = 5 * 1000 = 5000 metres


Explanation:


  • When converting kilometres to metres, we need to multiply the number of kilometres by 1000 because 1 kilometre is equal to 1000 metres.

  • Therefore, 5 kilometres is equal to 5 * 1000 = 5000 metres.


Correct Answer:


  • C: 5000 metre


Therefore, the correct answer is option C: 5000 metre.

A pendulum swings backwards and forwards passing through Y, middle point of the oscillation. The first time the pendulum passes through Y, a stopwatch is started. 
The twenty-first time the pendulum pass through Y, the stopwatch is stopped. The reading is T. What is the time period of the pendulum? 
  • a)
    T/40
  • b)
    T/21
  • c)
    T/20
  • d)
    T/10
Correct answer is option 'D'. Can you explain this answer?

Anagha Nambiar answered
The time taken to complete one oscillation is called the time period of a pendulum.       

Here the time period is the time taken to move from Y to B then back to A and then to Y. The reading of stopwatch = T Number of oscillations = 10 
∴  Time taken 
 = T/10

Which unit is commonly used to measure distance?
  • a)
    Kilogram
  • b)
    Meter
  • c)
    Liter
  • d)
    Second
Correct answer is option 'B'. Can you explain this answer?

Focus Academy answered
The meter (option B) is the SI unit for measuring distance or length. Kilogram (option A) is the SI unit for mass, liter (option C) is the SI unit for volume, and second (option D) is the SI unit for time.

The height of a person is 1.65 m. Express it into cm and mm.
  • a)
    165 cm and 1650 mm
  • b)
    165 cm and 165 mm
  • c)
    160 cm and 1650 mm
  • d)
    160 cm and 1600 mm
Correct answer is option 'A'. Can you explain this answer?

Get Idea answered
The height of 1.65 metres can be converted to 165 centimetres and 1650 millimetres. This is because 1 metre equals 100 centimetres and 1000 millimetres. Thus, 1.65 metres equals 165 centimetres and 1650 millimetres.

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