31. A car travels 30 km at a uniform speed of 40 km/h and the next 30 km at a uniform speed of 20 km/h.
Find its average speed.
Answers
ANSWER
The total time for the journey is given as,
t=
v
1
d
1
+
v
2
d
2
=
40
30
+
20
30
=2.25hour
The average speed is given as,
v
avg
=
t
d
1
+d
2
=
2.25
30+30
=26.67km/h
Thus, the average speed of the car is 26.67km/h.
Answered By
Answer:
Explanation:
If an object has uniform motion, the speed is :
Speed = Distance/Time
The distance is 30 Km + 30 Km = 60 Km
To find the time, we need to modify the equation for speed.
Speed = Distance/Time
= Time = Distance/Speed
As there are two speeds, we will use Time = Distance/ Speed 1 + Speed 2
Using the values, the equation will be:
= Time = 60 km / 40 + 20 Km/h
= Time = 60 Km / 60 Km/h
= Time = (60 Km / 1 Km) / (60 Km/h / 1 km)
After cancelling Kilometers with Kilometers,
= Time = 60 / (60 / 1 h)
= Time = 1 h
After using the values in the formula for average speed,
Speed = 60 Km/h
One way to check this is to find the value for the time taken.
Time = Distance/Speed
= 60 Km / 60 Km/h
= 1 hr
I hope this helps you understand.