Question

find acceleration (m/sec²) of the body when speed changes from 20 km/hr to 30 km/hr in 10 secs.​

Answer 1

GIVEN :-

• Initial velocity(u) = 20 km/h

• Final velocity(v) = 30 km/h

• Time(t) = 10 s

TO FIND :-

The acceleration of the body in m/s².

FORMULA TO BE USED :-

v = u + at

SOLUTION :-

u = 20 km/h

⇒u = 20 * (5/18)

⇒u = 100/18

⇒u = 5.56 m/s

$\rule{130}{2}$

v = 30 km/h

⇒v = 30 * (5/18)

⇒v = 150/18

⇒v = 8.34 m/s

$\rule{130}{2}$

Now,

v = u + at

⇒a = (v - u)/t

Putting the known values :-

⇒a = (8.34 - 5.56)/10

⇒a = 2.78/10

⇒a = 0.278 m/s²             ---- Answer!

Answer 2

Answer:

$\frac{5}{18} \ m/s^{2}$

Explanation:

Given:

Initial velocity = u = $20 \ km/hr$

20 km/hr = $20 \times \frac{5}{18} = \frac{50}{9} m/s$

Final velocity = v = $30 km/hr$

30 km/hr = $30 \times \frac{5}{18} = \frac{25}{3} m/s$

Time = t = 10 seconds

To find:

Acceleration

Acceleration = $\frac{v-u}{t}$

Where:

v = final velocity

u = initial veloity

t = time

Acceleration = $\frac{\frac{25}{3}-\frac{50}{9} }{10}$

Acceleration = $\frac{\frac{75}{9}-\frac{50}{9} }{10}$

Acceleration = $\frac{\frac{25}{9}}{10}$

Acceleration = $\frac{25}{9} \times \frac{1}{10}$

Acceleration = $\frac{5}{18} \ m/s^{2}$

The acceleration of the body is equal to $\frac{5}{18} \ m/s^{2}$