Question

a body is projected vertically upward with initial velocity 80metre per second its velocity after 4 seconds​

Answer 1

$\huge{\bold{\underline{\underline{....Answer....}}}}$

$\huge{\bold{\underline{Given:-}}}$

u = 80 m/s.

t = 4 seconds.

v =?.

a = - g

(As it is thrown upward it moves up against the gravity)

$\huge{\bold{\underline{Explanation:-}}}$

According to First kinematic equation.

$\large{\bold{v = u + at}}$

Substituting the values.

$\large{v = 80 + (- 10) \times 4}$

$\large{v = 80 - 10 \times 4}$

$\large{v = 80 - 40}$

$\large{v = 40 m/s}$

$\huge{\boxed{\boxed{v = 40 m/s}}}$

So,the velocity after 4 seconds is 40 m/s.

Answer 2

Explanation:

Time of acent of the body Ta = u/g

Ta = 80/10

= 8sec

so the body will be at half the maximum height

velocity at half the max height

v= u+ (-a) t

v= 80 - 40

v = 40ms^-1