Question

A Truck at 54kmlhr slows down to 36 km/hr in 10s .find the retardation

Answer 1

Answer:

Given : Initial velocity = 54 km/hr

Final velocity = 36 km/hr

Time taken = 10 seconds.

To find : retardation

Calculation : First of all, convert the initial and final velocity unit to metres/second.

The. trick of doing this is to multiply the given data with 5/18.

Therefore initial velocity = 54km/hr

= 54 *(5/18)= 15 m/sec.

similarly, final velocity = 36 km/hr

= 36 *(5/18) = 10 m/sec.

Therefore ,

acceleration

= (final velocity -initial velocity)/time

= (10 -15)/10

= (-5)/10

= -0.5 m/sec^2

Therefore retardation is 0.5m/sec^2

Answer 2

Required Answer:

As per the provided question,we have:

• Intial velocity (u) = 54km/hr

→ 54 ×$\dfrac{5}{18}$

→ 3 × 5

→ 15m/s

• Final velocity (v) = 36km/h

→ 36 × $\dfrac{5}{18}$

→ 2 × 5

→ 10 m/s

• Time taken (t) = 10s

We have to find:

• Retardation

Let's solve it:

By the first equation of motion:

• v = u + at

→ 10 = 15 + ( a × 10 )

→ 10 = 15 + 10a

→ 10a = 10 - 15

→ 10a = -5

→ a = $\dfrac{-5}{10}$

→ a =$\dfrac{-1}{2}$ m/s²

Therefore, retardation is 1/2m/s².

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More information!

Equations of motion:

• v = u + at
• s = ut + ½at²
• v² – u² = 2as

Where,

• ★ v = final velocity = m/s
• ★ u = initial velocity = m/s
• ★ a = acceleration = m/s²
• ★ s = distance/displacement = m
• ★ t = time = sec

Remember that!

• When a body starts from rest, its initial velocity is 0.
• When a body comes to stop or applies breaks, its final velocity is 0.

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