# Math Help - Physics problems on Energy

1. ## Physics problems on Energy

1. A stone of mass 0.5 kg is projected vertically upwards with an initial velocity of 4.0ms^-1. What is its kinetic energy when it reaches a height of 0.5m?

2. http://i48.tinypic.com/iyj0a9.png (both questions)

I couldn't load the Physics Help Forums website. Hope posting in here is just as fine, since it says in the description 'chemistry and physics'.

2. ## Re: Physics problems on Energy

use conservation of energy principles in both questions ...

1. A stone of mass 0.5 kg is projected vertically upwards with an initial velocity of 4.0ms^-1. What is its kinetic energy when it reaches a height of 0.5m?
initial kinetic energy = gravitational potential energy + final kinetic energy

1. initial total mechanical energy - work done by friction = final total mechanical energy

$mgh_A - f \cdot \Delta x = mgh_B + \frac{1}{2}mv_B^2$

solve for $h_B$

2. you can answer this question