Menu Close

Question-90692




Question Number 90692 by I want to learn more last updated on 25/Apr/20
Commented by I want to learn more last updated on 25/Apr/20
Note:  V_A   =  3    and   V_B   =  5
$$\mathrm{Note}:\:\:\mathrm{V}_{\mathrm{A}} \:\:=\:\:\mathrm{3}\:\:\:\:\mathrm{and}\:\:\:\mathrm{V}_{\mathrm{B}} \:\:=\:\:\mathrm{5} \\ $$
Commented by mr W last updated on 25/Apr/20
which direction do V_A  and V_B  have?
$${which}\:{direction}\:{do}\:{V}_{{A}} \:{and}\:{V}_{{B}} \:{have}? \\ $$
Answered by mr W last updated on 25/Apr/20
Commented by mr W last updated on 25/Apr/20
using my own method:  length of string  2y_A +2y_B +y_C =L=constant  ⇒2(dy_A /dt)+2(dy_B /dt)+(dy_C /dt)=0  ⇒2V_A +2V_B +V_C =0  ⇒2a_A +2a_B +a_C =0  + direction is downwards (↓)    example:  V_A =−3 (↑)  V_B =5 (↓)  ⇒2(−3)+2×5+V_C =0  ⇒V_C =−4 (↑)
$${using}\:{my}\:{own}\:{method}: \\ $$$${length}\:{of}\:{string} \\ $$$$\mathrm{2}{y}_{{A}} +\mathrm{2}{y}_{{B}} +{y}_{{C}} ={L}={constant} \\ $$$$\Rightarrow\mathrm{2}\frac{{dy}_{{A}} }{{dt}}+\mathrm{2}\frac{{dy}_{{B}} }{{dt}}+\frac{{dy}_{{C}} }{{dt}}=\mathrm{0} \\ $$$$\Rightarrow\mathrm{2}{V}_{{A}} +\mathrm{2}{V}_{{B}} +{V}_{{C}} =\mathrm{0} \\ $$$$\Rightarrow\mathrm{2}{a}_{{A}} +\mathrm{2}{a}_{{B}} +{a}_{{C}} =\mathrm{0} \\ $$$$+\:{direction}\:{is}\:{downwards}\:\left(\downarrow\right) \\ $$$$ \\ $$$${example}: \\ $$$${V}_{{A}} =−\mathrm{3}\:\left(\uparrow\right) \\ $$$${V}_{{B}} =\mathrm{5}\:\left(\downarrow\right) \\ $$$$\Rightarrow\mathrm{2}\left(−\mathrm{3}\right)+\mathrm{2}×\mathrm{5}+{V}_{{C}} =\mathrm{0} \\ $$$$\Rightarrow{V}_{{C}} =−\mathrm{4}\:\left(\uparrow\right) \\ $$
Commented by I want to learn more last updated on 25/Apr/20
Thanks sir. I appreciate.
$$\mathrm{Thanks}\:\mathrm{sir}.\:\mathrm{I}\:\mathrm{appreciate}. \\ $$

Leave a Reply

Your email address will not be published. Required fields are marked *