A boy covers 50 km in 2 hours. In 40 minute, he will cover
Answers
Answer:
Let’s first calculate the magnitude of the velocity in km/h as the distance s is given in kilometers (50 km) and the time period t is given in hours (2 hours).
The magnitude of the velocity v is calculated by dividing the distance by the time period. In other words,
v=st=50 km2 h=25 km/h.
Now, to convert 25 km/h into some speed expressed in m/s, we make use of the definition that there are 1000 m in 1 km, which means that, in order to convert 25 km into m, we have to multiply 25 with 1000 (since we are not dealing with 1 but with 25 km).
v=25 km/h×1000 m=25000 m/h.
Now, let’s convert one hour to seconds. We know there are 60 minutes in one hour, and 60 seconds in one minute, which means there are 60 minutes×60 seconds=3600 seconds in one hour. So, now we can write
v=25000 m/3600 seconds=25000 m3600 s=7 m/s rounded to 1 significant figure.
Of course, we could have done these two steps in one go. So, for future reference, if you have to convert from km/h to m/s divide the speed in km/h by 3.6, as shown below:
v=25 km×1000 m1 h×3600 s=25 km1 h×1000 m3600 s=25 km1 h×3.6 s/m=7 m/s rounded to 1 significant figure.
Needless to say, one multiplies with 3.6 to obtain the km/h version of a m/s speed
Answer:
Letx consider, x= total distance covered by the car,
Time taken to complete the half distance with velocity v=40km/h,
t
1
=
2×40
x
=
80
x
hr. . . . .(1)
The time taken to complete another half distance with velocity u=60km/h
t
2
=
2×60
x
=
120
x
hr
The total time taken, t=t
1
+t
2
t=
80
x
+
120
x
=
48
x
hr
The average speed of the car,
v
avg
=
x/48
x
=48km/h
The correct option is B.
Step-by-step explanation:
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