A runner covers in and then in along a straight track

PHYSICS · Single correct · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

A runner covers

60\,\text{m}

30\,\text{s}

and then

40\,\text{m}

10\,\text{s}

along a straight track. She wishes to adjust only the time taken for the second

40\,\text{m}

so that her entire

100\,\text{m}

run is at a uniform speed equal to her speed during the first

60\,\text{m}

. Which of the following new times for the second part will achieve this? (a)

30\,\text{s}

(b)

18\,\text{s}

(c)

20\,\text{s}

(d)

25\,\text{s}