Instaneous power delivered by the force at any timet

  • Thread starter hauthuong
  • Start date
  • #1
15
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A force F acts on a particle of mass m. The particle starts from rest at t=0.
a) show that the instaneous power delivered by the force at any timet is (F^2/m)*t
Please give some directions how to solve it . Thank you
 

Answers and Replies

  • #2
299
0
Any idea where to start? (hint: what is the formula for power)
 
  • #3
15
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formula P=W/t or P=FV , and I don't know how to get t and and m involve in the formula
 
  • #4
38
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Think of the definition of velocity. [tex]v = a t[/tex]. And then use Newton's Seond Law for [tex]a[/tex].
 
  • #5
15
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Thank you very much, I got it, and I have another homework.
A raindrop (m=3.35*10^-5 kg) falls vertically at a constant speed under the influence of gravity and air resistance. after the drop has fallen 100m,
a)what is the work done by gravity?
b)the energy discipated by air resistance?
I got no clue for air resistance . Thank you
 
  • #6
165
0
If the raindrop where in the vacuum, the falling speed will not be constant. But when we do the experiment in a fluid, then a viscosity force appears and makes the raindrop or something else reach a constant speed. This force is proportional to the speed, so you may use newtonian physics...
 
  • #7
15
0
is it called resistive force?
 

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