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posted by  felix-Q on 11/4/2009 7:18:45 PM  |  status: Closed  |  Earned Karma: 67

urgent 1st year physics assignment question 2 !

Course Textbook Chapter Problem Needs by
General Physics N/A N/A N/A 11/4/2009 at 11:00:00 PM
Question Details:
8. [1pt]
A block of weight 35.0 N sits on an inclined plane, which makes an angle of 30.0° with the horizontal, as shown. The coefficient of kinetic friction between the block and the inclined plane is 0.340. A force applied parallel to the incline is just sufficient to pull the block up the plane at constant speed. What is the total work done on the block by all forces as the block moves a distance L = 2.01 m up the incline? Include only the work done after the block has started moving at constant speed, not the work needed to start the block moving from rest.
9. [1pt]
What is the work done by gravity?
10. [1pt]
What is the work done by the applied force?
11. [1pt]
What is the work done by the normal force?
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posted by watt (MNK) on 11/4/2009 7:22:35 PM  |  status: Live
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Response Details:
 
weight W = 35 N
angle θ = 30 degrees
The coefficient of kinetic friction between the block and the inclined plane is μ = 0.340
distance L = 2.01 m
(a). work done by gravity w= - W sin θ * L  
                                          = - 35.175 J
(b). Work done by applied force w ' = F * L  
Since it moves with constant speed ,applied frce = frciotnal force + W sin θ
                                                                     F = μW cos θ + W sin θ
                                                                        = 27.8 N
       So, w ' = 55.878 J
(c). work done by normal force w " = 0
Since normal force and  displacement are perpendicular to each other
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