- #1
Natbird
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The question:
A plank, of length L = 3.4 m and mass M = 22.0 kg, rests on the ground and on a frictionless roller at the top of a wall of height h = 1.60 m (see the figure). The center of gravity of the plank is at its center. The plank remains in equilibrium for any value of θ >= 59° but slips if θ < 59°.
a.Calculate the magnitude in Newtons of the force exerted by the roller on the plank when θ = 59°.
b.Calculate the magnitude in Newtons of the normal force exerted by ground on the plank when θ = 59°.
c.Calculate the magnitude in Newtons of the friction force between the ground and the plank when θ = 59°.
image: http://smg.photobucket.com/albums/v231/er1smesp00n/?action=view¤t=physics-1.gif
so I was just solving it as if it was a normal plank against wall style question
Sum of Forces in X direction=Force of roller - frictional force=0
Sum of Forces in Y Direction=Normal(upward force from ground)-mass(gravity)=0
Sum of Torques = Force of roller(height)-mass(gravity)cos(59°)(1.7)
I know these formulas are wrong since the Normal force does not equal mass*gravity like it should according to the equations above. How do you solve this problem.
A plank, of length L = 3.4 m and mass M = 22.0 kg, rests on the ground and on a frictionless roller at the top of a wall of height h = 1.60 m (see the figure). The center of gravity of the plank is at its center. The plank remains in equilibrium for any value of θ >= 59° but slips if θ < 59°.
a.Calculate the magnitude in Newtons of the force exerted by the roller on the plank when θ = 59°.
b.Calculate the magnitude in Newtons of the normal force exerted by ground on the plank when θ = 59°.
c.Calculate the magnitude in Newtons of the friction force between the ground and the plank when θ = 59°.
image: http://smg.photobucket.com/albums/v231/er1smesp00n/?action=view¤t=physics-1.gif
so I was just solving it as if it was a normal plank against wall style question
Sum of Forces in X direction=Force of roller - frictional force=0
Sum of Forces in Y Direction=Normal(upward force from ground)-mass(gravity)=0
Sum of Torques = Force of roller(height)-mass(gravity)cos(59°)(1.7)
I know these formulas are wrong since the Normal force does not equal mass*gravity like it should according to the equations above. How do you solve this problem.