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Physics/Work done concept


Dear Sir, my question is related to workdone, using the formula and the general concept. Formula for work doen = Force * diatnce cos of angle. If there is an object of any weight (suppose 20N) and it is ppulled with a force of 10 Newton for a distance of 20 meters horizontally, where the force makes an angle of 30 with the horizontal, then the work done will be = 10*20 cos 30 = 200*0.866= 173.20 joule (cos30=0866). Now if this force makes an angle of 90 degree with the horizonal (meaning to say that the force is applied  vertically upwards against the weight) and if the object is raised to a height of 20 meter, then by formula the work done will be = F*D Cos 90 = 10*20*0= 0 joule (cos90=0), but actually the object is lifted up to a certain height (20 m), then what is this lifting called in the language of science? Waitng for your valuable anwer. Regards

Simple enough, you only got your directions mixed up. The angle is relative to the direction of motion. Your first example is horizontal, so the angle is 30 degrees. Your second is vertical, so the applied for e is at zero degrees relative to the motion of lifting, not 90 degrees. So the cos(90)=1. Problem solved.


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Dr. Stephen O. Nelson


I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.


I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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