Question

A car acquires a velocity of 72km h^-1 in 10s starting from rest. Calculate acceleration , average velocity , distance travelled in this time

Answer 1

Given , Initial velocity u = 0

Final velocity v = 72km$\rm{{h}^{-1}}$

$\rm{ final \: velocity= \frac{72 \times 1000m}{60 \times 60s} = 20m {s}^{ - 1} }$

Time taken , t = 10 s

(i) Acceleration

$\rm{a = \frac{v - u}{t} }$

$\rm{a = \frac{(20 - 0)m {s}^{ - 1} }{10 \: s} }$

$\fbox{\rm{ \therefore{acceleration = 2m {s}^{ - 1} }}}$

(ii) Average Velocity

$\rm{average \: velocity \: = \frac{u + v}{2} }$

$\rm{average \: velocity \: = \frac{0+ 20}{2} \: m {s}^{ - 1} }$

$\fbox{ \therefore\rm{average \: velocity \: = 10 \: m {s}^{ - 1} }}$

(iii) Distance travelled

$\rm{distance \: travelled \: \: s \: = average \: velocity \times time}$

$\rm{s \: = (10m {s}^{ - 1} ) \times (10s)}$

$\fbox{ \therefore\rm{distance \: travelled \: = 100m}}$

Answer 2

Hey there !

Initial Velocity = u = 0

Final velocity = v = 72 km/hr = 72 x 5/18 = 20 m/s

Time = t = 10 sec

Acceleration = a

Equation of motion :-

v = u + at

20 = 0 + 10a

a = 20/10

a = 2 m/s²

displacement = distance traveled = s

Equation of motion :-

v² - u² = 2as

20² = 2 × 2 × s

400 = 4s

s = 400/4

s = 100 m

Average velocity = displacement / time

= 100 / 10

= 10 m/s

Hope this helps you !