A truck covers 40 km with an average speed of 80km/h. Then it travels another 40 km with an average speed of 40 km/h. The average speed of the truck for the total distanced covered is:

Average speed = 53.33 km/h

Explanation:

Below is the calculation for the average speed:

Given the average speed of for first 40 km = 80km/h

Time taken to cover the first 40 km = Total Distance / average speed

Time taken to cover the first 40 km = 40 / 80 = 0.5 hours

Given the average speed of for next 40 km = 40km/h

Time taken to cover the next 40 km = Total Distance / average speed

Time taken to cover the next 40 km = 40 / 40 = 1 hours

Now the average speed of the tuck to cover total distance:

Average speed = Total distance / Total time

Average speed = (40 + 40) / (0.5 + 1)

Average speed = 53.33 km/h

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s

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