The time, t, required to drive a fixed distance varies inversely as the speed, r. It takes 9 hr at a speed of 20 km/h to drive a fixed distance. How long will it take to drive the same distance at a speed of 23 km/h?

Time=7.84hrs

Explanation:

This is an inverse proportionality questions

Mathematically time t varies as 1/distance d

Hence T= dk/r

But speed r = distance/t

d= r*t= 9*20=180km/hr

We're k= constant of proportionality

At t=9hrs d=180km/hr

Hence k=r*t/d=20*9/1620=0.111

Finding t at at 1620km for 23km/hr

t=1620*0.111/23=7.84hrs

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.