Question

A car acquires a velocity of 72 km/h in 10 s starting from rest. Find

i) the acceleration

ii) average velocity

iii) the distance travelled in this time


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Answer 1

Answer :

72 km/hr in m/s,

$\sf=72\times\dfrac{5}{18}=\bf20m/s$

• Initial velocity = u = 0
• Final velocity = v = 20 m/s

i) Acceleration

• Acceleration = a

By first equation of motion,

⇒ v = u + at

⇒ 20 = 0 + 10a

⇒ 20 = 10a

⇒ 20/10 = a

∴ a = 2 m/s²

Acceleration is 2 m/s².

ii) Average Velocity

First we have to find the distance.

By third equation of motion,

⇒ v² - u² = 2as

⇒ (20)² - (0)² = 2 × 2 × s

⇒ 400 = 4s

⇒ 400/4 = s

∴ s = 100 m.

Average Velocity,

$\sf Avg.\ Velocity=\dfrac{Net\ Displacement}{Net\ Time}$

$\sf Avg.\ Velocity=\dfrac{100}{10}$

$\bf Avg.\ Velocity=10\ m/s.$

Average Velocity is 10 m/s.

iii) Distance trsvelled

We got the answer above this question.

Distance travelled is 100 m.

Answer 2

Answer:

1) Acceleration is 2 m/s².

2) Average Velocity is 10 m/s.

3) Distance travelled is 100 m.

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