FRICTION

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Corey Hubbard
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8 www.akhieducatio.com RICTION. A mooth block i releaed at ret o a 45 iclie ad the lide a ditace d. The time take to lide i time a much to lide o rough iclie tha o a mooth iclie.

1 8 RICTION. A mooth block i releaed at ret o a 45 iclie ad the lide a ditace d. The time take to lide i time a much to lide o rough iclie tha o a mooth iclie. The coefficiet of frictio i μ k = b) μ k = c) μ = d) μ =. Aertio (A): Agle of repoe i equal to the agle of limitig frictio. Reao (R): Whe the body i jut at the poit of motio, the force of frictio i thi tage i called limitig frictio. Both aertio ad reao are true ad reao i the correct explaatio of aertio b) Both aertio ad reao are true but reao i ot the correct explaatio of aertio c) Aertio i true but reao i fale d) Both aertio ad reao are fale 3. Three block of mae m, m ad m 3 kg are placed i cotact with each other o a frictiole table. A force i applied o the heaviet ma m ; the acceleratio of m 3 will be m b) m + m c) m + m 3 d) m + m + m A block B i puhed mometarily alog a horizotal urface with a iitial velocity v. If μ i the coefficiet of lidig frictio betwee B ad the urface, block B will come to ret after a time v gμ 5. The limitig frictio i b) g μ v alway greater tha the dyamic frictio b) alway le tha dyamic frictio c) equal to the dyamic frictio d) ometime greater ad ometime le tha the dyamic frictio c) g v d) v g

www.akhieducatio.com 6. The coefficiet of tatic frictio, μ, betwee block A of ma kg ad the table a how i the figure i.. What would be the maximum ma value of block B o that the two block do ot move?

2 6. The coefficiet of tatic frictio, μ, betwee block A of ma kg ad the table a how i the figure i.. What would be the maximum ma value of block B o that the two block do ot move? The trig ad the pulley are aumed to be mooth ad ma le ( g = m ) kg b) 4.kg c).kg d).4kg 6 7. A body of ma kg i placed o rough horizotal plae. The coefficiet of frictio betwee body ad plae i.. The body will move i forward directio, if = 5N b) body will move i backward directio with acceleratio.6m, if force = 3N c) body will be i ret coditio, if = 3N d) both a ad c are correct 8. Which of the followig tatemet i ot true? The coefficiet of frictio betwee two urface icreae a the urface i cotact are made rough b) The force frictio act i the directio oppoite to the applied force c) Rollig frictio i greater tha lidig frictio d) The coefficiet of frictio betwee wood ad wood i le tha 5 9. What i the maximum value of force uch that the block, how i the arragemet N b) N c) N d) 5N

3 4 A firema of ma 6kg lide dow a pole. He i preig the pole with a force of 6N. The coefficiet of frictio betwee the had ad the pole i.5, with what acceleratio will be firema lide dow ( g = m ) m b).5m c) m d) 5m. It i eaier to roll a barrel tha pull it alog the road. Thi tatemet i ot poible b) ucertai c) fale d) true Iclied Plae. A cubical block ret o a iclied plae of coefficiet of frictio μ = / 3 the agle of icliatio o that the block jut lide dow the iclied plae? 3 b) 6 c) 45 d). What hould be If the coefficiet of frictio of a plae iclied at 45 i.5. The acceleratio of a body lidig freely o it will be m b) m c) 9.8m d) 4.8m 4. The force required to jut move a body up a iclied plae i double the force required to jut prevet it from lidig dow. If θ i the agle of frictio ad φ i the agle which the plae make with the horizotal the taφ = taθ b) taφ = 3taθ c) taφ = taθ d) taθ = 3taφ KEY ) a ) b 3) d 4) a 5) a 6) d 7) d 8) c 9) a ) d ) d ) a 3) a 4) b

4 Whe frictio i abet a = giθ = at... () i Whe frictio i preet a = giθ μk gcoθ = at... ii ( ) HINTS rom Eq (i) ad (ii) a t = a t Or a t = a ( t ) ( t = t ) Or a = a a giθ μk gcoθ Or = = a giθ Or μk = or μ k = 3. a force applied = = total ma m + m + m 3 4. μ mg = ma v v Or μmg = m or t = t μ g 6. Let the ma of the block B i M. I equilibrium, T Mg = T = Mg (i) If block do ot move, the T = f

www.akhieducatio.com Where f = frictioal force = μr = μmg T = μ mg (ii) Thu, from Eq (i) ad (ii), we have Mg = μ mg Or M = μ m Give, μ =., m = kg M =.x =.4 kg 7.

5 Where f = frictioal force = μr = μmg T = μ mg (ii) Thu, from Eq (i) ad (ii), we have Mg = μ mg Or M = μ m Give, μ =., m = kg M =.x =.4 kg 7. or movig the body, applied force hould be greater or equal to limitig frictio (i.e. μ N limitig frictio i f = μn = μmg =. x x 9.8 = 3.9N ice applied force = 5N, o body tart to move i forward directio b) here, applied force i leer tha limitig frictio. So, body doe ot move c) the reao i ame a (b) hece, (d) i correct 9. f = μr ). The = μ W + co 6 ( i 6 ) Subtitutig μ = ad W = 3 3

6 = N. Net dowward acceleratio weight frictio force = ma ( mg μr) = m. Cocept = = = 5m 6 Topic 5: Iclied Plae. taθ = μ taθ = 3 taθ = ta 3 Agle of icliatio θ = 3 3. The acceleratio of the body lidig o the iclied plae i give by 9.8 = g(iθ μ co θ ) = 9.8(i 45.5co 45 ) = m 4. mg(iφ+ μco φ) = mg(iφ μco φ) taφ = 3μ But μ = taθ Hece, taφ = 3taθ

04 - LAWS OF MOTION Page 1 ( Answers at the end of all questions )

04 - LAWS OF MOTION Page 1 ( Answers at the end of all questions ) 04 - LAWS OF MOTION Page ) A smooth block is released at rest o a 45 iclie ad the slides a distace d. The time take to slide is times as much to slide o rough iclie tha o a smooth iclie. The coefficiet