Homework Help: physics

Posted by ekaterina on Monday, November 28, 2011 at 6:12pm.

A 68 student consumes 2500 Cal each day and stays the same weight. One day, he eats 3500 Cal and, wanting to keep from gaining weight, decides to "work off" the excess by jumping up and down. With each jump, he accelerates to a speed of 3.4 before leaving the ground.

physics - Damon, Monday, November 28, 2011 at 6:32pm
Kinetic energy of jump = (1/2) m v^2
= (1/2)(68)(3.4)^2 = 393 Joules

.25(3500-2500) = 250 food calories to burn
1 food calorie (1000 physics heat calories) = 4184 Joules

250 Cal * 4184 J/Cal = 1,046,000 Joules

so
1,046,000/393 = 2661 Jumps
Luckily saw whole problem before the 25% efficiency part was deleted - Damon, Monday, November 28, 2011 at 6:34pm
I was working on your final version.
physics - Ms. Sue, Monday, November 28, 2011 at 6:58pm
Sorry, Damon. I thought she'd posted exactly the same question a dozen times, so I deleted the extras.
physics - Damon, Monday, November 28, 2011 at 6:59pm
LOL - does not matter. I had already copied the last one.

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