Question

Q1.A car starts from rest and attains a speed of 72 km/h in 5 seconds. Find the acceleration of the car.​

Answer 1

Step-by-step explanation:

✬ Acceleration = 5 m/s² ✬

Explanation:

Given:

• A car stars from rest.
• Final speed of car is 72 km/h.
• Time taken to attain final speed is 5 seconds.

To Find:

What is the acceleration of the car ?

Formula to be used:

v = u + at

Solution:

Let the acceleration of the car be a m/s².

First of all lets change km/h to m/s by multiplying with 5/18.

➟ v = 72 × 5/18

➟ v = 4 × 5 = 20 m/s

Here we have

u = 0 m/s

v = 20 m/s

t = 5 s

a = a m/s²

Putting all the values on above formula

⟹ v = u + at

⟹ 20 = 0 + a × 5

⟹ 20 = 5a

⟹ 20/5 = a

⟹ 4 m/s² = a

Hence, the acceleration of the car is 4 m/s².

Answer 2

$\huge { \red { \boxed{ \blue{ \boxed{ \bf \purple{5m/ {s} }}}}}}$

Step-by-step explanation:

GIVEN :-

• Starting speed (u) = 0 m/s or 0 km/h
• Final Velocity (v) = 72 km/h
• Time taken (t) = 5 s

TO FIND :-

• The acceleration

SOLUTION :-

We have to change 72 km/h to m/s

[to change km/h to m/s, multiply km/h by 5/18]

$\bf72km {h}^{ - 1} = \cancel {72}^{ \: 4} \times \frac{5}{ \cancel{18}} \\ \\ \bf = 4 \times 5 {mps}^{ - 1} \\ \\ \bf = 20 {mps}^{ - 1}$

.

Now,

Acceleration (a) -

$\bf a = \frac{v - u}{t} \\ \\ \bf = \frac{20 - 0 {mps}^{ - 1} }{5s} \\ \\ \bf = \frac{20 {mps}^{ - 1} }{5s} \\ \\ \bf= {4mps}^{ - 2}$

So,

The acceleration is 4m/s².

.

Hope it helps.