Mechanical Engineering - Engineering Mechanics - Discussion

Option: A is correct.

Just ready to move a body condition is IMPENDING MOTION (angle of inclined = angle of friction).

Static friction condition is (angle of inclined < angle of friction).

@All.

When a body is inclined with an angle ( suppose a ) then force required to move it up is the function of the angle of inclination and the friction. The equation is given by p = w( sin(a) + u cos (a) ). Where u = tan@ = Fr (frictional force)/ Reaction.

Now put u = tan@ in equation of p and take the value of a > @, a=@, and a<@ and you can observe p is minimum when a= @.

Now come to the logic that one of you have given above that " just think logically if something is placed horizontally and something is at an incline at which place force require is more" definitely at horizontal. Having said so you should also keep in mind that frictional angle has nothing to do with inclination. It also applies when the body is at the plane horizontal surface. Frictional angle is an angle between reaction and static frictional force component. You can't relate anything with anything :) And if you are interested in doing so just give me the reason why Boyles law become invalid when you inflate a balloon. Why pressure and volume both increases even though Temp is Constant.

The force required to move a body up an inclined plane will be minimum, when the angle it makes with the inclined plane is less than the angle of friction. This ensures that the force applied is just enough to overcome the frictional force and initiate motion without unnecessary resistance.

Here we are talking about angle at which have to apply the force to minimise it.

I agree with you @Mastwaseem.

Thank you @Ritu raj that really helped.

Agree @Bharat_kumar.

You must ignore the friction first for the min value of P with ignoring that remains

P= W sin(a) only.
As (a) become smaller P becomes smaller,
So the current answer is Option B only.

If the inclination of the plane, with the horizontal, is less. The angle of friction, the body will be automatically in equilibrium. If in this condition, the body is required to be moved upwards or downwards, a corresponding force.

Is required, for the same. But, if the inclination of the plane is more than the angle of friction, the body will move down. And an upward force (P) will be required to resist the body from moving down the plane.

Option C is the correct answer.

Option B is the correct answer.

Dear friends. please read the question carefully.

1) First angle that is the angle of inclination and angle of friction is the same thing.
2) The second angle they r talking about is the angle of pulling of force with respect to the plane.
It must be equal to angle plane for less effort to pull it.