No calculus required!

Classical Mechanics Level 4

From the figure (sorry for "paint" quality XD). A mass m m is placed on a frictionless surface with angle θ 1 \theta_{1} to the vertical line. It's pulled by constant force F = 42.25 newton F = 42.25 \text{ newton} using a massless string such that the mass don't float when it's pulled. After I stop pulling this mass when the rope does the angle θ 2 \theta_{2} to the vertical line, find the amount of work done by F F in joules \text{joules} at the point when I stop pulling it.

Details:

  • Pulleys are very strong that they always stay still, massless, and frictionless.
  • g = 9.8 m s 2 g = 9.8 \frac{m}{s^{2}}
  • m = 25.1 k g m = 25.1 kg
  • This problem is from my physics teacher.


The answer is 84.5.

Samuraiwarm Tsunayoshi by Samuraiwarm Tsunayoshi , 22, Thailand

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3 solutions

Abi Krishnan
Oct 4, 2014

The work done is F* the parallel component of the displacement. The parallel component of the displacement can be found by finding the change in the length of the string from theta 1 to theta 2, because that's how much string the force F pulls. Thus delta x = sqrt(12^2+9^2) - sqrt(12^2+5^2) = 2m. Work = 2*42.25 = 84.5 Joules

8 Helpful 1 Interesting 2 Brilliant 0 Confused

Brilliant! \textbf{Brilliant!}

Harsh Poonia - 1 year, 10 months ago
Nivedit Jain
Mar 1, 2018

1 Helpful 0 Interesting 1 Brilliant 0 Confused
Topper Forever
Mar 11, 2018

Too easy, not at all level 4, should be level 0, hahaha 😂😂😂 #topper forever 😎😎

0 Helpful 0 Interesting 0 Brilliant 0 Confused

Overconfident forever

Sahil Silare - 3 years, 2 months ago

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