In which of the following cases of motion,are the distance moved and the magnitude of displacement equal?

$(a)$ Define uniform circular motion.
$(b)$ Ram goes for a morning walk in a circular park daily. He completes one revolution of the park in $4$ minutes. Find his speed if the diameter of the park is $420\, m$.
$(c)$ Draw velocity$-$time graph for uniform motion along a straight line. How can you find the distance covered by a body from this graph?

What can you say about the motion of an object whose distance-time graph is:
$(i)$ a straight line,parallel to the time axis?
$(ii)$ a straight line passing through the origin making an angle with the time axis?

$A$ cyclist driving at $36 \, km \, h^{-1}$ stops his cycle in $2 \, s$ by the application of brakes. Calculate $(i)$ retardation $(ii)$ distance covered during the application of brakes.

Four cars $A$,$B$,$C$ and $D$ are moving on a levelled road. Their distance versus time graphs are shown in the figure. Choose the correct statement.

An object is dropped from rest at a height of $150 \, m$ and simultaneously another object is dropped from rest at a height of $100 \, m$. What is the difference in their heights after $2 \, s$ if both objects drop with the same acceleration? How does the difference in heights vary with time?