Pushing moves the block horizontally and the block has no rotation assuming low friction. Sufficient friction between the table and block would produce a net torque which would cause the block to flip.
When is the net torque acting on an object zero, and yet the net force is nonzero? Physics Rotational Motion Static Equilibrium. Amory W. Aug 24, This happens more frequently than the converse. Does zero net force imply zero net torque? Ask Question. Asked 5 years, 7 months ago. Active 5 years, 5 months ago. Viewed 6k times. Improve this question. Kyle Oman MikeCheng MikeCheng 29 1 1 silver badge 5 5 bronze badges. Add a comment. Active Oldest Votes.
No, it doesn't. M is a measure of the resistance an object has toward being linearly accelerated. I is a measure of the resistance an object has toward being angularly accelerated about an axis. We have so far learned the concepts of torque T and angular acceleration a.
What is left to learn here is the mass moment of inertia I. Mass moment of Inertia I :. Consider a thin ring of mass M and radius R that is attached to a vertical rod via a number of say 3 weightless spokes as shown in Fig. Also , consider another ring that has the same mass M but a radius of 2R and with weightless spokes as in Fig.
Mass Moment of Inertia of a Thin Ring:. The mass moment of inertia of a thin ring about its centroidal axis is given by. The "centroidal axis" is an axis that is perpendicular to the plane of a ring and passes through its center. The vertical rods in the above figures are centriodal axes.
Mass Moment of Inertia of a Solid Disk:. A solid disk of radius R may be thought as a combination of infinite number of thin rings which radii range from zero to R. Of course, as we go from the inner rings to the outer ones, each ring has more mass as well as a greater radius that makes its corresponding I increasingly greater.
To find the total I for all rings, calculus must be employed and integration performed. Again, this is good only for finding I about the the centriodal axis of a disk. Note that for a solid disk, M is several times greater than that of a thin ring of the same radius and material.
Example A 1. A above. The apparatus is initially at rest. The vertical axis is then given a twist by a constant net torque of 6. Find a the angular acceleration of the spinning ring, and b the angle it travels within the 2. Assume frictionless rotation. Example A kg solid disk of radius 0. A force of N is applied tangent to its outer edge for 1. Calculate a the mass moment of inertia of the disk, b the torque applied as a result of the applied force, c the angular acceleration of the disk, and d its angular speed and the linear speed of points on its edge at the end of the 1.
Torque of F about the axle at C. In straight line motion , K. In rotational motion, the equivalent is obviously K. In straight line motion, linear momentum is Mv. In rotational motion, angular momentum is I w. Example In Example 12, find the K. Problem: Solve Example 12 , with the assumption that the axle imposes a frictional torque of 78Nm. Since the externally applied force of N to the rim creates a CCW torque to rotate the wheel in CCW direction, the frictional torque that always opposes the direction of rotation, acts CW.
Problems: [Apply 3 significant figures to all numbers]. Find a its mass moment of inertia, b its angular acceleration, and c its final speed. The friction at its axle is negligible. Find a its mass moment of inertia about its centroidal axis. Find b the resulting applied torque. If the friction at its axle generates a counter torque of 0. The wheel then slows down and eventually comes to stop due to the frictional torque present at its axle. Calculate e the angular deceleration, and f the stopping time.
The starter electric motor gets engaged with the teeth on the edge of this wheel to crank the engine.
0コメント