Help on physics homework
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Help on physics homework

[From: ] [author: ] [Date: 11-09-13] [Hit: ]
7N/9.8m/s/s= 19.......
it's about Force. it says:
you are using a 250 cm lever to lift a rock with a mass of 100 kg. Then it gives an equation of Fr x dr = Fe x de, where " Fr " is the weight of the rock, " dr " is the distance from the rock to the pivot (40 cm), Fe is your pushing force, and " de " is the distance from the end of the lever where you push to the pivot (210 cm). What is the force of the effort? How much mass would you have to place on the end of the lever to balance the weight of the rock?
thank you!

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the weight of the rock = mass x g = 100kg x 9.8m/s/s = 980N

so you have 40cm*980N = 210 cm *applied force

applied force = 186.7N

if you applied this force by placing a rock, you would need a rock with mass

mass = weight / g = 186.7N/9.8m/s/s = 19.0 kg
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