Can a particle be accelerated

$(i)$ if its speed is constant ?

$(ii)$ if its velocity is constant ?

Which of the following is not a vector ?

A circular cycle track has a circumference of $314\, m$ with $A B$ as one of its diameter. $A$ cyclist travels from $A$ to $B$ along the circular path with a velocity of constant magnitude $15.7\, m s ^{-1}$. Find the

$(a)$ distance moved by the cyclist.

$(b)$ displacement of the cyclist, if $A B$ represents north$-$south direction.

$(c)$ the average velocity of the cyclist.

A frog hops along a straight line path from point $'A^{\prime}$ to point ${ }^{\prime} B ^{\prime}$ in $10\, s$ and then turns and hops to point ${ }^{\prime} C^{\prime}$ in another $5\, s$. Calculate the average speed and average velocity of the frog for the motion between $(a)(A)$ to $(B)(b)(A)$ to $(C)($ through $B)$

A person standing at $A$ goes to $B$ by following any of the paths $1,2$ or $3 .$ Which path we can measure to find the average velocity ?