Question

20)A car is moving on a straight road from
A to B for first one-fourth distance with
speed 40 m/s and the next half with speed
80 m/s and last one fourth with speed
120 m/s. Then the average speed of the
car will be
a)49.26 m/s
b)90.46 m/s
c)68.57 m/s
d)54.26 m/s



please answer fast...give right answer otherwise I will report ...​

Answer 1

Answer:

68.57 m/s

Explanation:

First you have to find out total time taken by car and then put all values which are given in question and you can easily find out your answer

Answer 2

Answer:

The average speed of the car will be equal to 68.57m/s.

Therefore, the option (c) is correct.

Explanation:

Average speed of the car is the ratio of total distance travelled by the car to total time taken.

Average speed = Total distance/ total time                                ...............(1)

Consider tat the total distance travelled by the car is 'S'.

The speed of the car for first one-fourth distance (1/4)S is = 40m/s

Then the time taken t₁ = distance/speed

$t_{1}=\frac{S/4}{40}$

$t_{1}=\frac{S}{160}$

The speed of the car for the next half distance (1/2)S is = 80m/s

Then the time taken t₂ = distance/speed

$t_{2}=\frac{S/2}{80}$

$t_{2}=\frac{S}{160}$

The speed of the car for last one-fourth distance (1/4)S is = 120m/s

Then the time taken t₃ = distance/speed

$t_{3}=\frac{S/4}{120}$

$t_{3}=\frac{S}{480}$

The total time = t₁ + t₂ + t₃ = $\frac{S}{160} +\frac{S}{160} +\frac{S}{480}$

Total time $=S(\frac{3+3+1}{480} )=\frac{7S}{480}$

Substitute the values in equation no. (1);

Average speed $=\frac{S}{7S/480}=\frac{480}{7}$

Average speed of the car = 68.57m/s

Therefore, the average speed of the car will be equal to 68.57m/s.