A student walks along a straight track in two successive stages

PHYSICS · Multi-part · GCSE · Physics · Forces · Forces

Problem

A student walks along a straight track in two successive stages. In the first stage she travels a distance

d_1

to the right in time

t_1

. In the second stage she immediately turns around and travels a distance

d_2

to the left in time

t_2

. Take motion to the right as positive. (i) Derive an expression for the average speed

v_{\text{avg}}

for the entire walk in terms of

d_1, d_2, t_1,

and

t_2

. (ii) Derive an expression for the average velocity

\bar v

for the entire walk using the same symbols. (iii) Obtain the mathematical condition on

d_1

and

d_2

for which the average velocity becomes zero, and interpret this condition physically.