Question

11. A car acquires a velocity of 72km per hour in 10 seconds starting from rest. Find (a) the acceleration, (b) the average velocity, and (c) the distance travelled in this time.​

Answer 1

Solution :

Here , initial velocity , u=0 , time taken , t=10s

final velocity , v=72kmh=72×1000m60×60s=20m/s

(a) acceleration , a=v−ut=20−010=2m/s2

b)average velocity , vav=u+v2=0+202=10m/s

( c ) distance travelled , s=?

From v2−u2=2 as, s=v2−u22a=(20)2−02×2=100m

Answer 2

Given :-

Final velocity = 72 km/h

Time taken = 10 sec

To Find :-

The acceleration.

The average velocity.

The distance travelled in this time.​

Solution :-

We know that,

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

Using the formula,

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

Given that,

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

Time taken (t) = 10 sec

Initial velocity (u) = 0

Substituting their values,

20 = 0 + a (10)

a = 20/10

a = 2 m/s²

Therefore, the acceleration is 2 m/s².

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

Acceleration (a) = 2 m/s²

Substituting their values,

(20)²- (0)² = 2(2) (s)

400=4s

s = 400/4

s = 100 m

Therefore, the distance travelled is 100 m.

By the formula,

$\underline{\boxed{\sf Average \ velocity= \dfrac{Displacement}{Time} }}$

Given that,

Displacement (s) = 100 m

Time taken (t) = 10 sec

Substituting their values,

= 100/10

= 10 m/s

Therefore, the average velocity is 10 m/s.