Question

A twig from a tree drops from a 200 m high cliff on to a beach below. During its fall, 40% of the
twig’s energy is converted into thermal energy.
What is the speed with which the twig hits the beach?

Answer 1

So what do you have so far?

Answer 2

It's a conservation of energy problem - can you set up an expression for the energy of the twig before its dropped, and then when it reaches the ground?

Answer 3

thank you, i got the answer:)

Answer 4

Very nice ^_^

Answer 5

ahh. At first the twig is freely falling so no initial force is applied..
then simply the thermal energy is created by friction of air. so any object after acheiving its terminal velocity there is no furthur increase in velocity...
you take some mass of twig, and area pof the twig as A, let the gravitational constant be the universal one....
and ... you can get density of air and drag co-efficient from internet.
apply all these to a simple formula of terminal velocity as root of [(2*m*g)/(density*A*Drag Co-eff)]

finally you will get the terminal velocity of the twig... and as you said the 40% of the energy is converted to some other...
so the 60% of the terminal velocity will be your twig velocity before hitting the ground....

Keep Asking & Answering.......

Answer 6

yeah thank you