Question

A stone of mass 0.4 kg is thrown vertically upward with speed 9.8 m/s. Find the kinetic energy and potential energy after 1s.

Answer 1

Answer:

K.E. = 0

P.E. = 19.2J (approx)

Please acknowledge if you've understood it or not

Explanation:

m = 0.4kg

u = 9.8 m/s

t = 1s

So we have to find the velocity after 1s,

v = u +at

=> v = 9.8 + ( - 9.8) x 1 (g is taken negative coz going against gravity)

=> v = 0 (So K.E. is 0)

Now, initial K.E. = Final P.E. (Conservation of energy)

So, use 1/2 x m x v^2

1/2 x 0.4 x 9.8^2 = 19.2J (approx)

Note: You can do it the long way by using P.E. = mgh so you find the height using the motion formulas but as a wise man once said,

"Work smarter not longer"