# College Physics Help

posted by .

A thin rod (length = 1.10 m) is oriented vertically, with its bottom end attached to the floor by means of a frictionless hinge. The mass of the rod may be ignored, compared to the mass of the object fixed to the top of the rod. The rod, starting from rest, tips over and rotates downward. (a) What is the angular speed of the rod just before it strikes the floor? (Hint: Consider using the principle of conservation of mechanical energy.)(b) What is the magnitude of the angular acceleration of the rod just before it strikes the floor?

Sorry - I would show some work but I have no clue how to even attempt this. Please help :(

• College Physics Help -

Not sure how to apply the principle of conservation of mechanical energy.

• College Physics Help -

(a) With no mass in the rod and all of the mass (M) at the top, the total kinetic energy just before it strikes the floor is
(M/2)V^2 = (M/2)(w*L)^2 = M g L
M cancels out, and the angular velocity w is
w = sqrt(2g/L) = 4.2 rad/s

(b) Just before impact, the mass atop the rod is accelerating at rate g. Angular acceleration before impact = a/L = g/L = 8.9 rad/s^2

## Similar Questions

1. ### rotational mechanics

a thin rod of length 2R and mass M is standing vertically on a perfectly smooth floor. the state of equilibrium in which the rod at rest is unstable and the rod falls. FInd the trajectories that the various points of rod describe and …
2. ### Physics

A thin rod (length = 1.03 m) is oriented vertically, with its bottom end attached to the floor by means of a frictionless hinge. The mass of the rod may be ignored, compared to the mass of the object fixed to the top of the rod. The …
3. ### College Physics

A rod of mass 4.3 kg and length 4.3 m hangs from a hinge as shown in Figure P9.28. The end of the rod is then given a “kick” so that it is moving at a speed of 2.3 m/s. How high will the rod swing?
4. ### college physics

I don't know where to begin with this question. Could someone help me please?
5. ### Physics

A 2.5 m rod of mass M= 4. kg is attached to a pivot .8m from the left end so that it can rotate vertically. At the left end of the rod is a small object with mass m=1.5kg. A spring with a spring constant k=90N/m is attached to the …
6. ### physics

A thin rod of mass M and length L is lying on a frictionless table. It is given an impulse of 4.5 N*s by a force of magnitude F on one end at an angle of 35 degrees to the rod. How far will the center of mass of the rod travel when …
7. ### Physics

A thin rod (uniform density & thickness) has mass M and length L. It is attached to the floor at a fixed location by a friction-less hinge. The rod start at rest, balanced vertically on its hinge end. ______________________________________ …
8. ### College Physics

A thin rod (uniform density & thickness) has mass M and length L. It is attached to the floor at a fixed location by a friction-less hinge. The rod start at rest, balanced vertically on its hinge end. ______________________________________ …
9. ### physics

A thin rod (uniform density & thickness) has mass M and length L. It is attached to the floor at a fixed location by a friction-less hinge. The rod start at rest, balanced vertically on its hinge end. ______________________________________ …
10. ### Physics

A uniform rod of length L and mass M is held vertically with one end resting on the floor as shown below. When the rod is released, it rotates around its lower end until it hits the floor. Assuming the lower end of the rod does not …

More Similar Questions