A car accelerates from 30 km/hr to 65 km/hr in 30 seconds. What is it's acceleration?

Acceleration = (change in speed) / (time for the change).

= (35 km/hr) / (30 sec)

= 7/6 km/hr-sec.

To get rid of that ugly unit, and change the solution to a

more familiar unit of acceleration, we need to convert it

to the usual ' m/s² '. This is not a major operation.

(7/6 km/hr-sec) x (1000 m/km) x (1 hr/3600 sec)

= (7/6 x 1,000 : 3600) km-m-hr / km-hr-sec-sec

= 0.324 m/s² (rounded)

(This a rather gentle acceleration ... about 0.03 of a 'G' ...

so it would not mash you back into your seat in the car.)