10_02_Block_Ramp_2_other

# 10_02_Block_Ramp_2_other - N H,B W E,B = mg = 5(10) = 50N N...

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Physics 211 10/2 HW Handout Due Friday 10/4 Fall 2002 Block on a Ramp with different N H,B forces 1) A hand pushes on a 5.0kg block with a force of 30N directed parallel to the ramp. The coefficients of static and kinetic friction are μ s = 0.5 and μ k = 0.4 respectively. The ramp makes an angle of angle 24 ° with the horizontal. a) Draw a FBD of the block showing all the forces acting on the block. At this point you do not know about or F net or the acceleration. b) Find the magnitudes of all the forces (except friction) acting on the block. You will need to separate the Weight force into x and y components. Show your work. c) Find out whether the friction force is the static or kinetic type, and find its magnitude and direction. Show your reasoning. d) Find F net , magnitude and direction. Show your work. e) For each of the following, find the friction force, the net force, and acceleration. i) N H,B = 10N ii) N H,B = 45N Moving up ramp iii) N H,B = 45N Moving down ramp 5.0kg N H,B = 30N 24 ° y x a = ? F net = ? W x W E,B W y
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Unformatted text preview: N H,B W E,B = mg = 5(10) = 50N N H,B = 30N W x = 50Sin24 ° = 20N N R,B = W y = 46N, 2 nd Law, a y = 0 W y = 50Cos24 ° = 46N N H,B + W x = 10N This is the force we must compare to the max static to see if it moves. f R,B Max = μ s N R,B = 0.5(46) = 23N and 10N is NOT enough force to cause slippage. N R,B No slippage, no a, F net = 0, f R,B = 10N You can now draw this force on the FBD. N H,B + W x = 10N (opposite of part c.) Less than f R,B Max so static, F net = 0, f R,B = 10N (opposite of part d.) N H,B + W x = 25N Greater than f R,B Max so kinetic, f R,B = μ k N R,B = 0.4(46) = 18.4N directed down the ramp, opposite the velocity . F net = N H,B + W x + f R,B = 6.6N N H,B + W x = 25N Greater than f R,B Max so kinetic, f R,B = μ k N R,B = 0.4(46) = 18.4N directed up the ramp, opposite the velocity . F net = N H,B + W x + f R,B = 43.4N a = F net /m = 6.6/5 = 1.3m/s 2 speeding up a = F net /m = 43.4/5 = 8.7m/s 2 slowing down...
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## This note was uploaded on 12/21/2010 for the course PHYS Physics 21 taught by Professor Larrywatson during the Fall '08 term at North Dakota.

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