00:02
Hi, here in this given problem, this is the rough horizontal surface and this is a block of mass m kept over it.
00:17
A force is being applied to push it.
00:22
At an angle, theta with the horizontal mass of the block that is given as m is equal to 25 kilogram.
00:33
Angle theta that is 25 degree initially speed that is 0 force applied to start the motion that is 17 newton maximum force required to start the motion and this is to start the motion and the force required to keep it in motion that is just 50 newton okay now two components of this force, horizontal component, which will be pushing the block in forward direction, f -cos theta, and vertical force f -sign theta.
01:31
Weight of the block, m .g, acting vertically down, and force of friction, f -s or fk, whatever it will be, will be acting towards left.
01:42
And this is the distance moved by the block.
01:51
In this question number 15 for the block just to start moving this forward force f cos theta that should be equal to force of static friction, means mu s times the normal reaction and normal reaction of the surface.
02:23
N that will be equal to m g acting vertically down minus sorry plus this f sine theta it will also be added f sine theta so mu s will be given by an expression f cost theta divided by m g plus f sine theta plugging in the known values for f this is 70 newton multiplied by cost 25 degree divided by m g 25 multiplied by 9 .8 plus f again 70 sine 25 degree so this mu s will be given by 63 .44 in numerator divided by first term 245 plus second term 29 .58...