Question

please explain your answer​

Answer 1

EXPLANATION

• GIVEN

Body is vertically upward with a velocity = u

after 1 and 7 second it cross reference point

at a height h

TO FIND VALUE OF U.

As we know that body is project upward

we can apply,

newton 2nd law of kinematics

h = ut - 1/2gt^2

for 1 seconds

h = u(1) - 1/2 g

h = u - g/2 .... (1)

for 7 seconds

h = u(7) - 1/2 g (7) ^2

h = 7u - 49g / 2 .... (2)

from equation (1) and (2)

we get,

u - g/2 = 7u - 49g/2

24g = 6u

4g = u

g = 10 m/s^2 [GIVEN]

Therefore,

u = 40 m/s = ANSWER