Question

You are driving home from school steadily at 95 km/h for 180km. It then begins to rain and you slow to 65 km/h. You arrive home after driving 4.5 h. (a) How far is your hometown from school? (b) What was your average speed?

Answer 1

Answer:

Explanation:

Given

Person travel 180 km with $v_1=95\ km/h$

and slow down to $v_2=65\ km/h$ due to rain

time taken to cover 180 km is

$t_1=\dfrac{180}{95}$

$t_1=1.89\ hr$

total time $T=4.5\ hr$

suppose $t_2$ is the time for which it travels with $v_2=65\ km/h$

$t_2=T-t_1$

$t_2=4.5-1.89$

$t_2=2.61\ hr$

so distance travel during this time $d_2=v_2\times t_2$

$d_2=65\times 2.61$

$d_2=169.65\ km$

total distance $d=180+d_2$

$d=180+169.65$

$d=349.65\ km$

(b)Average speed

$v_{avg}=\dfrac{Distance}{time}$

$v_{avg}=\dfrac{349.65}{4.5}$

$v_{avg}=77.7\ km/h$