A bus decreases its speed from $80\, km\, h^{-1}$ to $50 \,km h ^{-1}$ in $4\, s$. Find the acceleration of the bus.
Given $v=50 km h ^{-1}=50 \times \frac{5}{18}=\frac{125}{9} m s ^{-1}$
$u=80 km h ^{-1}=80 \times \frac{5}{18}=\frac{200}{9} m s ^{-1}$
$t=4 s$
Using the expression $v=u+a t,$ we have
$a=\frac{v-u}{t}=\frac{125-200}{9 \times 4}=-2.083 m s ^{-2}$
Write true or false for the following statements
In one$-$dimensional motion, the average velocity and the instantaneous velocity are unequal.
Define acceleration. State a relationship connecting $u, v, a$ and $t$ for an accelerated motion. Give an example of a motion in which acceleration is uniform.
Distinguish between terms speed and velocity.
What is the slope of the displacement $-$ time graph when the body has uniform motion ?
The graph given below is the distance$-$time graph of an object.
$(i)$ Find the speed of the object during first four seconds of its journey.
$(ii)$ How long was it stationary ?
$(iii)$ Does it represent a real life situation ? Justify your answer.