Mechanical Engineering - Engineering Mechanics - Discussion

If the angle of repose is equal to the angle of friction body require minimum force to move.

But both the forces are equal then how the object move?

For the object to be in a dynamic condition the applied force must be greater than the reaction force.

@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.

Nice, Thanks @Ritu Raj.

Boyle's law states that at constant temperature FOR A FIXED MASS, the absolute pleasure and the volume of a gas are inversely proportional. While inflating a balloon mass is not fixed as we add air in it.

Angle of friction means the angle of the plane in which the body tends to over come the friction force.

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.

Option B is the correct answer.

Option C is the correct answer.

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.