Question

​a body falls from 80m its time of descent is ? [when g=10m/s2]

Answer 1

Here, the formula is S is equal to ½ g x t (square) added to i x t

In this case, u is equal to 0

And we have to find t or time

Then the formula would be 80 equal to ½ (10) x t square

T square is 16

So t will be 4 seconds

Answer 2

Answer:

Distance travelled(h) = 80 m

g = -10 m/s2

Initial velocity of the body= u

by third equation of motion i.e.

     2gh= v2- u​2   ( v = 0 as body finally comes to rest)

     u or initial velocity = 40 m/s  

Now,  

By first equation of motion  

v = u + gt

0 = 40 - 10t

t = 4 seconds

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