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

Answer:

(a) 2m/s^2.

(b) 10m/s.

(c) 100m.

Explanation:

please refer to the image.

Answer 2

Explanation:

Given:-

• Initial velocity (u) = 0m/s [ Car stars from rest]

• Final velocity (v) = 72km/hr

• Time (t) = 10 sec

To Find:-

• Acceleration (a)

• The average velocity

• The distance travelled (s)

Solution:-

72km/hr = $72 \times \dfrac{5}{100}$ = 20m/s

Final velocity (v) = 20m/s

Using 1st equation of motion:-

$\sf \implies v = u + at$

$\sf \implies 20 = 0 + a(10)$

$\sf \implies 10a =20$

$\sf \implies a = \dfrac{20}{10}$

$\sf \implies a = 2m/s^2$

$\sf \therefore \underline{\:\: \underline{\: Acceleration = 2m/s^2\:}\:\:}$

$\sf (b) \: Average \: velocity = \dfrac{Final\: velocity + Initial\: velocity}{2}$

$\sf \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \dfrac{0 + 20}{2}$

$\sf \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \dfrac{20}{2}$

$\sf \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 10m/s$

$\sf \therefore \underline{\:\: \underline{\: Average \: velocity = 10m/s^2\:}\:\:}$

$\sf (c) \: Distance = Average \: velocity \times Time$

$\sf \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 10 \times 10$

$\sf \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 100$

$\sf \therefore \underline{\:\: \underline{\: Distance \: travelled = 100m\:}\:\:}$