ࡱ> Root Entryp|YrRASH`/ContentsPage 1  !"#$%3Root Entryp|YrRASHGContents*Page 1  &'()+,-./012CPicPage CPicLayer CPicFrameCPicTextS hTimes New Roman(Practice Test (2 of them) CPicShape 9'BTimes New Roman(1. A +8 C charge is at the origin. It required 40 mJ to move a small charge from the point (120cm,0) to the point (40cm,0) What is the value of the small charge?CPicPage CPicLayer CPicFrame?Layer 1OLW NG;  ,%Td1 Times New Roman(We'll need these two equations: hTimes New Roman(V=kq/r W=qV%BTimes New Roman(Ok... those V's in the equations are not the same. The first is the V at a given point. The second is the difference in the V's at the two points. Let's start by calculating the V's at each point seperately.p  Times New Roman(VTimes New Roman(1Times New Roman(=9*10Times New Roman(9Times New Roman((8*10Times New Roman(-6 Times New Roman()/1.2 VTimes New Roman(2Times New Roman(=9*10Times New Roman(9Times New Roman((8*10Times New Roman(-6Times New Roman()/.4W  Times New Roman(VTimes New Roman(1 Times New Roman(=60000 VTimes New Roman(2Times New Roman(=180000% &B,Times New Roman(Ok... now we can calculate the difference. VTimes New Roman(2Times New Roman(-VTimes New Roman(1Times New Roman(=180000-60000=120000. Now we have the V that we can use for the work equation. We also know the total work is 40 mJ... so we can plug and chug now.M Times New Roman(40*10Times New Roman(-3 Times New Roman(=q(120000)  Times New Roman(q=3.33*10Times New Roman(-7 Times New Roman(C 'B!Times New Roman(4. A +2 C charge with mass 3*10Times New Roman(-20Times New Roman( kg changes speeds from 7*10Times New Roman(6 Times New Roman( m/s to 5*10Times New Roman(6eTimes New Roman( m/s in 6 mm. What was the Electric field in this region and what was its direction? {ignore gravity}W t'%-n3 7$iX  Times New Roman(Equations:m$ hTimes New Roman(KEhTimes New Roman(AhTimes New Roman(+Fs=KEhTimes New Roman(BhTimes New Roman( F=Equ% 9Times New Roman(Since F=Eq, we can substitute it in. We end up with 1/2mvTimes New Roman(2 Times New Roman(+Eqs=1/2mvTimes New Roman(2Times New Roman(. Now we plug in numbers.  Times New Roman(1/2(3*10Times New Roman(-20Times New Roman()(7*10Times New Roman(6Times New Roman()Times New Roman(2Times New Roman(+E(2*10Times New Roman(-6 Times New Roman()=1/2(3*10Times New Roman(-20Times New Roman(CPicPage CPicLayer CPicFrameCPicTextS hTimes New Roman(Practice Test (2 of them) CPicShape 9'BTimes New Roman(1. A +8 C charge is at the origin. It required 40 mJ to move a small charge from the point (120cm,0) to the point (40cm,0) What is the value of the small charge?LW NG;  ,%Td1 Times New Roman(We'll need these two equations: hTimes New Roman(V=kq/r W=qV%BTimes New Roman(Ok... those V's in the equations are not the same. The first is the V at a given point. The second is the difference in the V's at the two points. Let's start by calculating the V's at each point seperately.p  Times New Roman(VTimes New Roman(1Times New Roman(=9*10Times New Roman(9Times New Roman((8*10Times New Roman(-6 Times New Roman()/1.2 VTimes New Roman(2Times New Roman(=9*10Times New Roman(9Times New Roman((8*10Times New Roman(-6Times New Roman()/.4W  Times New Roman(VTimes New Roman(1 Times New Roman(=60000 VTimes New Roman(2Times New Roman(=180000% &B,Times New Roman(Ok... now we can calculate the difference. VTimes New Roman(2Times New Roman(-VTimes New Roman(1Times New Roman(=180000-60000=120000. Now we have the V that we can use for the work equation. We also know the total work is 40 mJ... so we can plug and chug now.M Times New Roman(40*10Times New Roman(-3 Times New Roman(=q(120000)  Times New Roman(q=3.33*10Times New Roman(-7 Times New Roman(C 'B!Times New Roman(4. A +2 C charge with mass 3*10Times New Roman(-20Times New Roman( kg changes speeds from 7*10Times New Roman(6 Times New Roman( m/s to 5*10Times New Roman(6eTimes New Roman( m/s in 6 mm. What was the Electric field in this region and what was its direction? {ignore gravity}W t'%-n3 7$iX  Times New Roman(Equations:m$ hTimes New Roman(KEhTimes New Roman(AhTimes New Roman(+Fs=KEhTimes New Roman(BhTimes New Roman( F=Equ% 9Times New Roman(Since F=Eq, we can substitute it in. We end up with 1/2mvTimes New Roman(2 Times New Roman(+Eqs=1/2mvTimes New Roman(2Times New Roman(. Now we plug in numbers.  Times New Roman(1/2(3*10Times New Roman(-20Times New Roman()(7*10Times New Roman(6Times New Roman()Times New Roman(2Times New Roman(+E(2*10Times New Roman(-6 Times New Roman()=1/2(3*10Times New Roman(-20Times New Roman()(7*10Times New Roman(6Times New Roman()Times New Roman(2 F Times New Roman(E=-30 N/C8qS&wTimes New Roman(The answer is really 30 N/C. The negative sign tells you the direction of the electrical field. Since it is negative, it means that the field is in opposition to the charge. Therefore, if the charge is going right, the field is going left.3]  MTimes New Roman(And my mind is done thinking for the evening. Good luck on the test, Everyone! Times New Roman(-Ericl"/)Times New Roman(Don't forget... Times New Roman(F=maTimes New Roman( could come in handy... Times New Roman(F=mgTimes New Roman( too... Times New Roman(F=kx.Times New Roman(... I dunno... They could show up somewhere...?Layer 1O  CDocumentPage Page 1Scene 1Ca<\<-@8hhhhh Vector::Template"PublishFormatProperties::generator CColorDef3PfP0PHP`Px333(3f<03CH3F`3Hxf0f30ff(0f5Hf<`f@x3330333xf3d03]H3Z`3Xx3333303f3PPH33Px`33Px33Pf30f33PHff3(PHf3<x`f3Cxf3Ffff`f03f0ffx0fkHfd`f`x3f033fPH3ffxPH3fdx`3f]x3fZff0f3fPHfff`ffP0xffPxffPH3HfHxH̙n`hx3H33x`3fx`3xx`3̙kx3dfHf3x`ff0xfx0xf̙dxf]`3`f``x`px3`33x3fx3x3xx3nf`f3xffxfxfxxfkx3xfxxxxx3x333f333xfxf3fffffxxH3 HfH(H2`8x`3 `f`̙`(`0xx3xfxx x(xPx3H33x`f3x`3(x`35x3<3`33xf3 x̙3x3(x323x33f3 333(xfH3fx`ff0xf(0xf<xfCf`3fxffx̙fxf(xf5fx3ffff ff((xH3x`f0x̙PPP`3xfx̙P̙(P<x3f̙(xx`3xfxPxPd`3xfx̙PPx3f(xx3fxx3f̙xx3f)(7*10Times New Roman(6Times New Roman()Times New Roman(2 F Times New Roman(E=-30 N/C8qS&wTimes New Roman(The answer is really 30 N/C. The negative sign tells you the direction of the electrical field. Since it is negative, it means that the field is in opposition to the charge. Therefore, if the charge is going right, the field is going left.3]  MTimes New Roman(And my mind is done thinking for the evening. Good luck on the test, Everyone! Times New Roman(-Ericl"/)Times New Roman(Don't forget... Times New Roman(F=maTimes New Roman( could come in handy... Times New Roman(F=mgTimes New Roman( too... Times New Roman(F=kx.Times New Roman(... I dunno... 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