Question

Answer the question plz

Answer 1

Explanation:

option 2 is the correct answers

distance covered in the time is slow down

Answer 2

Provided that:

• Initial velocity = 90 kmph
• Final velocity = 18 kmph
• Time taken = 2.5 seconds

To calculate:

• The acceleration
• The distance

Solution:

• The acceleration = -8 m/s sq.
• The distance = 87.5 m

Knowledge required:

• SI unit of acceleration = m/s²
• SI unit of velocity = m/s
• SI unit of time = sec
• SI unit of distance = m

Using concepts:

• Formula to convert kmph-mps
• Formula to find acceleration
• Second equation of motion

Using formulas:

• Kmph to mps,

• 1 kmph = ${\sf{\dfrac{5}{18} \: mps}}$

• Acceleration,

• ${\sf{a \: = \dfrac{v-u}{t}}}$

• Second equation of motion,

• ${\sf{s \: = ut \: + \dfrac{1}{2} \: at^2}}$

Where, a denotes acceleration, u denotes initial velocity, s denotes displacement or distance or height, t denotes time taken and v denotes final velocity

Required solution:

~ Firstly let us convert kmph-mps!

Converting 90 kmph-mps first!

⇒ 90 · 5/18

⇒ 5 · 5

⇒ 25 mps

• Henceforth, converted!

Now converting 18 kmph-mps!

⇒ 18 · 5/18

⇒ 1 · 5

⇒ 5 mps

• Henceforth, converted!

Therefore,

• Initial velocity = 25 mps
• Final velocity = 5 mps

~ Now let's calculate acceleration!

⇒ a = (v-u)/t

⇒ a = (5-25)/2.5

⇒ a = -20/2.5

⇒ a = -200/25

⇒ a = -40/5

⇒ a = -8 metre per second sq.

⇒ Acceleration = -8 m/s sq.

⇒ Retardation = -8 m/s sq.

• Henceforth, solved!

~ Now let's find out the distance!

⇒ s = ut + ½ at²

⇒ s = 25(2.5) + ½ · -8(2.5)²

⇒ s = 62.5 + ½ · -8(6.25)

⇒ s = 62.5 + 1 · -4(6.25)

⇒ s = 62.5 + 1 · 25

⇒ s = 62.5 + 25

⇒ s = 87.5 m

⇒ Distance = 87.5 metre

• Henceforth, solved!