Question

With a starting speed of 30 kph at point A, a car accelerates uniformly.after 18 min,it reaches point B 21 km from A . find the acceleration of the car 1mm/sec^2

Answer 1

Given :

Initial speed of the car at point A:

u= 30 kph

=$30\times\frac{5}{18} \frac{m}{s}$

=The time car takes  to reach point B:

= 18 min

 $=18\times 60 s\\=1080 s$

Distance the car travels to reach point B:

S = 21 km

 = 21000 m

To Find :

Acceleration of the car in $\frac{m}{s^{2} }$ = ?

Solution :

The equation we have for the relation among acceleration, time,distance  and speed :

$S= ut +\frac{1}{2} \times at^{2}$

So putting the given values of u, S and t in above equation we get acceleration (a) as :

$21000= \frac{25}{3} \times 1080 + \frac{1}{2} a\times 1080 \times 1080\\\\21000 - 9000 = 583200\ti\frac{x}{y} mes a\\12000= 583200\timesa\\a=\frac{9000}{583200} \\\\a= 0.021 \frac{m}{s^{2} }$

So the acceleration of the car is $0.021 \frac{m}{s^{2} }$