Question

The roller has a mass of 45 kg and a diameter of 1.39 m. The height of the step is h = 0.10 m. Calculate the minimum force P required to pull the roller over the step.

http://www.learning.physics.dal.ca/dalphysicslib/Graphics/Gtype14/hibb5-49a.gif

Answer 1

I get 3.11e+01 for the angle which is right (that was easy) but I need help finding P!!

Answer 2

Use the conception of Projectile.

Answer 3

Sorry I don't quite understand that approach? Projectile motion?

Answer 4

@hba Can you help please

Answer 5

Don't we have to use moments (or torque)

Answer 6

help

Answer 7

no one here is helpful

Answer 8

yes man you are right we have to use torque or the technique of topling in a new way
just look at the diagram and please let me know, wheather i am helpful or not

if we see the directions of the components of all the forces, only teh cos comp. of p and cos comp of mg are producing torque and that too in the oposite direction.
so for the cyl. to come up on the step, the torque of mg cos theta should balance the torque of p cos theta.
to find the torque of p cos theta, we see the perpendicular distance from our ref. pt. i.e. A(i apologize i didn't specify it earlier).
we get the perpendicular distance= R-h
so torque due to cos component of force p=p(cos theta) x (R-h)
and torque due to cos component of mg= mg(cos theta) x R (perp. distance of the force from our ref. point A is R).
equate both the torques and you'll get the answer as
532.56N