Slide 1 : P. K. BHARTI, I.I.T. KHARAGPUR Friction
(Problems)
06.07.2010 © 2007-10 P K Bharti, IIT Kharagpur
Slide 2 : P. K. BHARTI, I.I.T. KHARAGPUR NECRT
Problems
15.06.2010 © 2007-10 P K Bharti, IIT Kharagpur
Slide 3 : P. K. BHARTI, I.I.T. KHARAGPUR © 2007-10 P K Bharti, IIT Kharagpur
Slide 4 : P. K. BHARTI, I.I.T. KHARAGPUR © 2007-10 P K Bharti, IIT Kharagpur
Slide 5 : P. K. BHARTI, I.I.T. KHARAGPUR © 2007-10 P K Bharti, IIT Kharagpur
Slide 6 : P. K. BHARTI, I.I.T. KHARAGPUR © 2007-10 P K Bharti, IIT Kharagpur H C Verma
Problems
15.06.2010
Slide 7 : P K BHARTI, IIT KHARAGPUR 7 Q A particle of mass m is resting on a horizontal surface. The static and kinetic friction coefficients between block and surface are m1and m2 respectively. Find the magnitude of friction acting on the block.
Ans: Zero.
Explanation:
Idea here is that the block is stationary.
Therefore, static friction is acting on the block.
As, there is no applied force in the horizontal direction.
Therefore, magnitude of friction force = applied force = 0 m
Slide 8 : P K BHARTI, IIT KHARAGPUR Q. Solve previous example again if the block rests on an inclined plane making angle q with horizontal.
SOLUTION:
Body is resting so static friction is acting.
Its direction will certainly upward the
incline(why??)
We draw FBD of block.
Now, we draw our coordinate system .
Resolve mg.
Along x-axis:
mg sinq – f = 0
? f = mg sin q. [Ans]
[Surprise!!!, we did not used any formula for friction, FBD done all]. 8 m y x N f mg mg cosq mg sinq q q
Slide 9 : P K BHARTI, IIT KHARAGPUR 9 Q A body of mass 2 kg is lying on a rough inclined plane of inclination 300. Find the magnitude of the force parallel to the incline needed to make the block move (a) up the incline (b) down the incline. Coefficient of static friction = 0.2
Slide 10 : P K BHARTI, IIT KHARAGPUR 10 Q Consider the situation shown in figure. Calculate (a) acceleration of 1 kg blocks, (b) the tension in the string connecting 1 kg blocks and (c) the tension in the strings attached to 0.50 kg.
Slide 11 : P K BHARTI, IIT KHARAGPUR 11 Q The friction coefficient between the board and the floor shown in figure is µ. Find the maximum force that the man can exert on the rope so that the board does not slip on the floor.