Question

5.
A motor vehicle travelled the first third of a
distance s at a speed of v,=10 kmph, the second
third at a speed of v,20 kmph and the last
third at a speed of v,=60 kmph. Determine
the mean speed of the vehicle over the entire
distance s.
1) 15 kmph
3) 10 kmph
2) 12 kmph
4718 kmph with explanation
​

Answer 1

Answer:

Let the total distance traveled be s.

Hence the time taken for first third of the distance= t

1

=

v

1

s/3

Similarly, the time taken for second third of the distance= t

2

=

v

2

s/3

and the time taken for last third of the distance= t

3

=

v

3

s/3

Hence the mean speed over the distance=

t

1

+t

2

+t

3

s

=

v

1

1

+

v

2

1

+

v

3

1

3

=18km/h