Question

usain bolt accelerates at a maximum rate of 2m/s². he has a top speed of 10m/s. it starts from rest and participates in a 100m race. find the time taken to finish the race .<br />hi friends <br />Answers please..please... ​

Answer 1

Answer:

12.5 seconds

Explanation:

Given :

• Acceleration of usain bolt = a = 2 m/s²

• Final velocity of usain bolt = v = 10 m/s (As it is the top speed under acceleration)

• Distance to be covered = s = 100 metres

• Initial velocity of usain bolt = u = 0 m/s

To find :

• Time taken to complete the race

First we need to find the time taken by usain bolt to reach a speed of 10 m/s

Using the first equation of motion :

V=u+at

10=0+2×t

10=2t

t = 5 seconds

Now we need to find the distance travelled during this acceleration

S=0×5+½×2×25

S=0+25

S=25 metres

Now 75 metres with a speed if 10 m/s

Time = distance / speed

Time = 75/10

Time = 7.5 seconds

Total time taken = 5+7.5

Total time taken = 12.5 seconds

The total time taken is 12.5 seconds

Answer 2

Given:-

• Initial velocity =0m/s

• Acceleration =2m/s²

• Final velocity =10m/s

• Distance covered =100m

To Find:-

• Total Time taken to finish the race.

Solution :-

By using 1st equation of motion

➦ v = u+ at

➭ 10 =0+2×t

➭ 10 = 2×t

➭t = 10/2

➭ t = 5 s

and now,

☛ s =ut +1/2 at²

☛ s = 0 × 5 +1/2× 2 × 5×5

☛s = 25 m

Now, remaining distance 100-25=75m

it is given that he covers distance at speed of 10m/s

➦time =distance /speed

➭ time =75/10

➭ time =7.5s

∴Total time taken to finish the race is 5+7.5=12.5 s.