Home » Ask Physics » A body covers a distance of 20 m in 7th sec and 24 m in the 9th sec. How much shall it cover in 15s ?

A body covers a distance of 20 m in 7th sec and 24 m in the 9th sec. How much shall it cover in 15s ?

“A body covers a distance of 20 m in 7th s and 24 m in the 9th s. How much shall it cover in 15s ?”  – Raghav posted this question.

 

Answer: From the eqn for displacement in the nth second,

S_{n}=u + a\left ( n-\frac{1}{2} \right )

For the displacement in the 7th sec, we get,

20= u+a(7-\frac{1}{2})=u+a(\frac{13}{2}) …………………….. (1)

For the displacement in the 9th sec,

24= u+a(9-\frac{1}{2})=u+a(\frac{17}{2}) ……………………..(2)

(2)-(1) gives

24-20 = 2a

or a = 2 m/s2

Substituting for a in (1),

u = 7 m/s

Substituting, u= 7 m/s, a = 2 m/s2 and t = 15 sec in the eqn,
S = ut + \frac{1}{2} a t^{2}

we get S= 7 x 15 + 0.5 x 2x 15 x 15 = 105+225=330m

 

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Hits so far @ AskPhysics

  • 2,274,296 hits

You may also be interested in

Subscribe to AskPhysics via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

Join 4,341 other subscribers

September 2021
M T W T F S S
 12345
6789101112
13141516171819
20212223242526
27282930  

Learn Self Defence Techniques online

%d bloggers like this: