Acceleration and Retardation

Acceleration is defined as the change in velocity per unit time. The negative acceleration is called retardation or deceleration. This note provides us with an information about acceleration and retardation.

Summary

Acceleration is defined as the change in velocity per unit time. The negative acceleration is called retardation or deceleration. This note provides us with an information about acceleration and retardation.

Things to Remember

  • Acceleration is defined as the change in velocity per unit time. Acceleration is measured in m/s2.
  • The negative acceleration is called retardation or deceleration. Its unit is same as acceleration.
  • Equations involving displacement, initial velocity, final velocity, acceleration and time of motion of a moving body are equations of motion.
 

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Subjective Questions

Q1:

Answer the following questions:

How is the candidate selected?

 


Type: Short Difficulty: Easy

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Answer: <p>Candidates are selected through competition.</p>

Q2:

Answer the following questions:

For what purpose has the advertisement been published?


Type: Short Difficulty: Easy

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Answer: <p>For "Miss Tourism World" the advertisement has been published.</p>

Q3:

Answer the following questions:

What are the things that candidate should submit along with their application?


Type: Short Difficulty: Easy

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Answer: <p>A short bio-data one close-up photograph (B2 size) and one full-length photograph (postcard size) should submit by the candidate along with their application.</p>

Q4:

Answer the following questions:

Mention the necessary requirements for the candidate?


Type: Short Difficulty: Easy

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Answer: <p>Thenecessary requirements for the candidate are:</p> <p>Nepalese citizen only</p> <p>Age 19-27</p> <p>Minimum Education 10+2</p> <p>Full-length height 5 ft. 4 inch</p> <p>Fluent in English (spoken &amp; written)</p> <p>Unmarried</p>

Q5:

Fill in the blanks with appropriate words or phrases from the advertisement:

This firm has been successful in coordinating Nepalese participation for ______.


Type: Very_short Difficulty: Easy

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Answer: <p>Miss earth 2002</p>

Q6:

Fill in the blanks with appropriate words or phrases from the advertisement:

The successful candidate will be offered an opportunity to participate in the contest for ______.


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Answer: <p>competition</p>

Q7:

Fill in the blanks with appropriate words or phrases from the advertisement:

Candidates should send their applications to ______.


Type: Very_short Difficulty: Easy

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Answer: <p>Himalayan Trade Promotion Concern P.Ltd. Lazimpat, Kathmandu.</p>

Q8:

Match the following:

Column A                                  Column B

biodata                                       the action of taking part in something

model                                          a public entertainment consisting of a procession of people in costume 

pageant                                       a record of age, qualification, interest, experience etc.

participation                                 a person employed to display something like clothes etc.


Type: Very_short Difficulty: Easy

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Answer: <table width="235"><tbody><tr><td>Column A</td> <td>Column B</td> </tr><tr><td>biodata</td> <td>a record of age, qualification, interest, experience etc.</td> </tr><tr><td>model</td> <td> a person employed to display something like clothes etc.</td> </tr><tr><td>pageant</td> <td> a public entertainment consisting of a procession of people in costume</td> </tr><tr><td>participation</td> <td> the action of taking part in something</td> </tr></tbody></table>

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Acceleration and Retardation

Acceleration and Retardation

Acceleration

Acceleration is defined as the change in velocity per unit time. Acceleration is measured in m/s2.

=

Retardation

The negative acceleration is called retardation or deceleration. Its unit is same as acceleration.

Example:

1. Car starts from rest. After 5 seconds, its velocity becomes 10 m/s. Then find its acceleration.

Initial velocity (u) = 0

Final velocity (v) = 10 m/s

Time taken (t) = 5 s

Acceleration (a) =?

Or,

Or,

∴ a = 2m/s2

2. The Car which starts from the rest has an acceleration of 0.3 m/s2. After 1 minute what will be its acceleration? What is the distance travelled by car?

Initial velocity (u) = 0

Time taken (t) = 1 min= 1 × 60 s = 60 s

Acceleration (a) = 0.3 m/s2

Final velocity (v) =?

Distanced travelled (s) =?

According to formula, v= u+ at

Or, v = 0 + 0.3 × 60

V= 18 m/s

∴ s =540 m

 

Equation of motion of uniform acceleration

Equations involving displacement, initial velocity, final velocity, acceleration and time of the motion of a moving body are equations of motion.

Considering a body moving in a straight line with uniform acceleration is shown in the figure.

Let,

Displacement = s

Initial velocity = u

Final velocity = v

Acceleration = a

Time taken = t

Relation between u, v, a and t

 

 

 

Or,

Or, at = v-u

∴ v= u + at ………….. (i)

This is the first equation of motion.

Relation between u,s, v and t

Or,

Or, \(\text{Average Velocity}=\frac{\text{Total Displacement(s)}}{\text{Total Time Taken(t)}}\)

Or,

 

 

As both, equation is equal

Or,

Or, 2s = (u + v)t

∴ ……………… (ii)

This is the second equation of the motion.

 

Relation between s, u, a and t

We already have,

V= u + at………….. (i)

s = (u + v)t…………… (ii)

Putting value of v from equation (i) in (ii)

Or,

Or, s =

Or, s = 2u×t + at × t× ½

∴ s = ut + ½ at2………………. (iii)

This is the third equation of motion.

Lesson

Velocity and Acceleration

Subject

Science

Grade

Grade 8

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