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# Conservation of energy?

Please answer these questions and explain your answers. Please show ALL work...

1. During the hammer throw at a track meet, an 8 kilogram hammer is accidentally thrown straight up. If 784 joules of work is done on the hammer to give it its vertical velocity, how high does it rise?

2. A skater on a lake pushes a 5.0 kilogram log to clear a skating area. If the skater does 600 joules of work on the log and the ice is nearly frictionless, what speed is given to the log?

thank you.

-asian_al

### 1 Answer

- 1 decade agoFavorite Answer
energy is laways conseverd and can be written two differnt ways: kinetic energy, or energy of motion is 1/2*M*V^2. Potential energy is M*g*h where g is gravity (9.8) and h is height in meteres. For the 1s tproblem, you know the total energy in the system (784 joules all the work done). You also know that at it's highest point, the hammer will not be moving at all so it will al be potential energy so you jsut do 784=8kg*9.8*h where you have to solve for h. h= 784/8/9.8 or 10 meteres. For the 2nd problem, all the 600 joules is put into the log as kinetic energy because it is moving and is at ground level so it has a height of zero. therefore, 600=1/2*5*v^2, where you have to solve for V^2. V^2=600*2/5 V^2 = 240 take the square root of 240 and V= 15.4919