Question

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A car acquires a velocity of 72km/h in 10 seconds starting from rest. Find (a) the acceleration (b) the average velocity (c) the distance travelled in this time.
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Answer 1

Answer:

acceleration = v-u/t where u=om/s and v =72m/s

72 ( 1000/3600) m/s = 20m/s , t = 10 sec.

a = v-u/t = 20-0/10 = 2m/s^2.

Explanation:

average velocity = v+u/2

= 20+0/2 = 10m/s^2.

distance = average velocity × time

= 10 × 10 = 100 m

Answer 2

Given :-

Initial velocity of the car = 0 m/s

Final velocity of the car = 72 km/h

Time taken by the car = 10 sec

To Find :-

The acceleration of the car.

The average velocity of the car.

Analysis :-

Here we are given with the initial velocity, final velocity and the time taken by the car.

Using the first equation of motion substitute the values given in the question accordingly and find the acceleration.

Then using the third equation of motion find the displacement of the car by substituting the values we got.

Finally, find the average velocity using it's respective formula.

Solution :-

We know that,

• a = Acceleration
• u = Initial velocity
• t = Time
• s = Displacement
• v = Final velocity

Using the formula,

$\underline{\boxed{\sf First \ equation \ of \ motion=v=u+at}}$

Given that,

Initial velocity (u) = 0 m/s

Final velocity (v) = 72 km/h = 20 m/s

Time (t) = 10 sec

Substituting their values,

⇒ 20 = 0 + a × 10

⇒ 20 = 10a

⇒ a = 20/10

⇒ a = 2 m/s

Therefore, the acceleration of the car is 2 m/s.

Using the formula,

$\underline{\boxed{\sf Third \ equation \ of \ motion=v^2-u^2=2as}}$

Given that,

Final velocity (v) = 20 m/s

Initial velocity (u) = 0 m/s

Acceleration (a) = 2 m/s

Substituting their values,

⇒ 20² - 0² = 2 × 2 × s

⇒ 400 = 4s

⇒ s = 400/4

⇒ s = 100 m

Therefore, the distance travelled in this time is 100 m.

Using the formula,

$\underline{\boxed{\sf Average \ velocity=\dfrac{Total \ displacement}{Total \ time} }}$

Given that,

Displacement (s) = 100 m

Time (t) = 10 sec

Substituting their values,

⇒ v = 100/10

⇒ v = 10 m/s

Therefore, the average velocity of the car is 10 m/s.