Question

an object starting from rest and travels 50 m in first 5 seconds and 400 m in next 10 seconds. what will be the velocity after 12 seconds from the start ?​

Answer 1

Given:

✭ Distance travelled in the first part = 50 m

✭ Time taken = 5 s

✭ Distance travelled in the second part = 400 m

✭ Time taken = 10 s

To Find:

◈ Velocity after 12 seconds

Solution

First we have to find the acceleration of the body

By the second equation of motion we know that,

s = ut + ½at²

The acceleration inthe first part is given by

➝ 50 = 0 × 5 + ½ × a × 25

➝ 12.5 a = 50

➝ a = 4 m/s²

The final velocity in the first part is given by

➳ v = u + at

➳ v = 0 + 4 * 5

➳ v = 20 m/s

Now we have to find the find the acceleration in second part

➢ 400 = 20 × 10 + ½ × a × 100

➢ 400 = 200 + 50a

➢ a = 200/50

➢ a = 4 m/s²

Here we can see that the acceleration in both parts is same

Hence velocity is given by,

»» v = u + at

»» v = 0 + 10 × 12

»» v = 120 m/s

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