16. An orange is thrown vertically upwards with
an initial velocity of 8 ms-1. (a) What will be the
velocity of orange when it returns to its starting
point? (b) How long will the orange take to reach
its starting point ?
Answers
Answer:
velocity of orange when it return to it's starting point = 8m/s in downward direction
t = 2*8/10 = 1.6sec
Explanation:
we can use newton's equation
v = u - at
s = ut - 1/2at^2
v^2= u^2 - 2as
here a = gm/s approx. 10m/s constant all over the world
here for time of flight s = 0 because s indicates displacement and displacement becomes zero when it reach to the ground.
ut = 1/2 gt^2
t = 2u/g
t = 2*8/10 = 1.6sec
now here v is the final velocity and u is the initially velocity
v^2 = u^2 - 2as
here further s is the displacement so it is zero when the orange reach to the ground
that is v^2 = u^2
so we can say that the orange will return to it's starting point with the same speed but different velocity
initially the velocity vector was in upward direction but at the time of hitting it's velocity vector is in downward direction
so velocity of orange when it return to it's starting point = 8m/s in downward direction
hope it is helpful.........................