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I hate Physics!

R

RecklaZ

Senior member
An athlete whose mass is 90.0 is performing weight-lifting exercises. Starting from the rest position, he lifts, with constant acceleration, a barbell that weighs 440 . He lifts the barbell a distance of 0.650 in a time of 2.10 .


Use Newton's laws to find the total force that his feet exert on the ground as he lifts the barbell. Take free fall acceleration to be 9.80 .

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I know F = ma and some other basic formulas. I know the answer must be logical. Can someone please point me in any direction that can help me solve this. Thanks.
 
Calculate the acceleration of the barbell. Then multiply by the mass to find the force. Add that to the force exerted by the athlete's mass (i.e. his mass times 9.8) and the bar mass times 9.8. Add the forces together for the total force exerted on the ground.
 
Originally posted by: Yossarian
the first rule of physics is that if you don't have units, you don't have anything.
Click to expand...

That's not exactly true. you can rig things so you don't have units 😀 😛

as a second rule: if you have the wrong units, you're screwed.
 
PM from RecklaZ:
Hi, u said (log (90.0 * 440 / 0.650)^2.1) mod 9.8

man that was easy.

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We havent touched logs yet, im in physics 1 w/cal now btw. Can u please help me out here bud.
Click to expand...
:thumbsup:
 
This is the same question with different numbers plugged.

An athlete whose mass is 93.0 is performing weight-lifting exercises. Starting from the rest position, he lifts, with constant acceleration, a barbell that weighs 500 . He lifts the barbell a distance of 0.700 in a time of 2.10 .

Use Newton's laws to find the total force that his feet exert on the ground as he lifts the barbell. Take free fall acceleration to be 9.80 .

The answer for this problem was 1430N, i'm trying to figure out my question by working backwards with this....... help?
 
Well the times are really unrealistic 😛 2.10 second? More like 0.50 of a second.

So do you understand?

Koing
 
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