Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision Both sides next revision
phy131studiof15:lectures:m2f15info [2015/11/03 15:47]
mdawber [Question 2 Solutions (23.7/35)]
phy131studiof15:lectures:m2f15info [2015/11/03 15:52]
mdawber [Question 2 Solutions (23.7/35)]
Line 139: Line 139:
 Now as this is the same distance the rope travels while the force $F$ is applied to it, the work done by $F$ is Now as this is the same distance the rope travels while the force $F$ is applied to it, the work done by $F$ is
  
-$W=Fd=7.5\times\0.5=3.75\,​\mathrm{J}$+$W=Fd=7.5\times0.5=3.75\,​\mathrm{J}$
  
 Alternatively you could compute the change in kinetic energy of both the pulley and the object and the change in the potential energy of the object. The sum of these is equal to the work done by $F$. Alternatively you could compute the change in kinetic energy of both the pulley and the object and the change in the potential energy of the object. The sum of these is equal to the work done by $F$.
Line 145: Line 145:
 $W=\frac{1}{2}\times\frac{1}{2}\times0.3\times0.15^2\times(\frac{2}{0.15})^2+\frac{1}{2}\times0.5\times2^2+0.5\times9.8\times0.5=3.75\,​\mathrm{J}$ $W=\frac{1}{2}\times\frac{1}{2}\times0.3\times0.15^2\times(\frac{2}{0.15})^2+\frac{1}{2}\times0.5\times2^2+0.5\times9.8\times0.5=3.75\,​\mathrm{J}$
  
-(e) (5 points) Once the object has reached a constant speed of $2\,​\mathrm{ms^{-1}}$ what force should I apply to the rope maintain that constant speed.+E. (5 points) Once the object has reached a constant speed of $2\,​\mathrm{ms^{-1}}$ what force should I apply to the rope maintain that constant speed.
  
-(f) (5 points) What is the angular velocity (in rpm) of the pulley while I am raising ​the object ​with a constant speed  of $2\,​\mathrm{ms^{-1}}$?​+If the pulley ​is not accelerated ​the tension ​in the rope attached to the object ​must be the same as that in the rope on the other side. As the object is not accelerating
  
-(g) (5 points) What is the angular momentum of the pulley while I am raising the object with a constant speed  of $2\,​\mathrm{ms^{-1}}$?​ Give both the magnitude and the direction (ie. left, right, up, down, in to the page, out of the page).+$T=mg$  
 + 
 +so  
 + 
 +$F=mg=0.5\times9.8=4.9\,​\mathrm{N}$ 
 + 
 +F. (5 pointsWhat is the angular velocity (in rpm) of the pulley while I am raising the object with a constant speed  of $2\,​\mathrm{ms^{-1}}$?​ 
 + 
 +$\omega=\frac{v}{r}=\frac{2}{0.15}=13.33\,​\mathrm{s^{-1}}$ 
 + 
 +To convert to rpm 
 + 
 +$\frac{13.33\times60}{2\pi}=127.3\,​\mathrm{rpm}$ 
 + 
 +G. (5 points) What is the angular momentum of the pulley while I am raising the object with a constant speed  of $2\,​\mathrm{ms^{-1}}$?​ Give both the magnitude and the direction (ie. left, right, up, down, in to the page, out of the page)
 + 
 +$L=I\omega=\frac{1}{2}mr^{2}\omega=\frac{1}{2}\times0.3\times(0.15)^{2}\times13.33=.045\,​\mathrm{kgm^{2}s^{-1}}$ 
 + 
 +Out of page from right hand grip rule.
  
  
phy131studiof15/lectures/m2f15info.txt · Last modified: 2015/11/03 23:14 by mdawber
CC Attribution-Noncommercial-Share Alike 3.0 Unported
Driven by DokuWiki