Question

44. A body thrown upward can reach
maximum height of 20m. The velocity
of body at a height of 15m is..... *
(1 Point)
8 m/s
12 m/s
10 m/s
15 m/s
in present in​

Answer 1

Answer:

Expert Answer:

m = 5 kg

u = 20 m/s (Initial velocity)

Initial kinetic energy,

K.E. = 1/2 mv2

K.E = 1/2 × (5) (20)2

K.E. = 1000 J

Thus, initial kinetic energy is 1000 J

Now, the speed with which the body is thrown is 20 m/s

Thus, height reached by body after 1 s is,

h = ut + 0.5 gt2

h = (20) (1) +0.5 (-10) (1) ... (negative sign for g indicates that the body is thrown against the gravity)

h = 15 m

P.E. = mgh = 5 × 10 × 15 = 750 J

The initial kinetic energy = total energy required to throw the body

Thus,

Kinetic energy after 1 s is,

T.E = P.E. + K.E. (after 1 s)

1000 J = 750 J + K.E. (after 1 s)

K.E (after 1 s) = 1000 - 750 = 250 J