Mechanical Engineering - Engineering Mechanics - Discussion

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.

Nice, Thanks @Ritu Raj.

@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.

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.

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

The correct answer is option A.

I think option A is right answer.

As per R.S. Kurmi book, the answer is option C.

@Bharath Kumar is right. So the answer is option B.

Yes, I agree @Bharat Kumar.

It will be easy and required a min force that can be applied to the body, if and only if the angle is less. It tends to move when the angle is equal to the frictional angle.