# physics (please check work)

Four identical particles, each with mass m, are arranged in the x,y plane like a cross. They are connected by light sticks to form a rigid body. If m=2.0kg and a=1.0 m the rotational inertia of this array about the y axis is:

work:
I know that
I= mr^2
I=(2.0kg)(1.0m)^2
I=2 kgm^2 for one body
for 4 x 2.=8
so I figured if is a rigid body all the mass would count for the Y axis array, I am not sure.

Consider four objects, each having the same mass and radius
1) a solid sphere
2) a hollow sphere
3) a flat disk in the x,y plane
4) a hoop in x,y plane
The order of increasing rotational inertia about an axis through the center of mass and parallel to the z axis.

Work:
I know that rotational inertia is smaller when mass is closer to the axis so I throught

1, solid sphere has mass distributed close to axis
3) a flask disk would have a mass closely ditributed to its axis
2) a hollow sphere would have points where the mass was distributed close to the axis near the top
4) the hoop contains only a ring of mass and may not be near the axis.

The first is right, if the rotational axis is the z axis, perpendicular to the xy plane. But about the y axis, you only have the two x masses rotating.

I would reverse 2,3 on inertia. The hollow sphere will have more near the axis than the flat disk.

1. 👍 0
2. 👎 0
3. 👁 281
asked by susane

## Similar Questions

1. ### physics

Six identical particles each of mass ‘m’ are arranged at the corners of a regular hexagon of side length ‘L’. If the masses of any two adjacent particles are doubled. The shift in the centre of mass is???

asked by Thousif on May 14, 2018
2. ### Math

Two particles X and Y joined by a rigit rod of negligible mass, move along a smooth horizontal plane. Particle X has mass 7.7kg and is pushed by an external force Fx of magnitude 73.01N. Particle Y has mass 5.68kg and is pulled

asked by Anonymous on September 7, 2012
3. ### Physics

Two particles A and B,are of equal mass,and moving towards each other,with speeds of 3m/sand 2m/s respectively and collide.Particle B then strikes a plane surface,which is perpendicular to its direction of motion and the

asked by Mercypraise on September 13, 2016
4. ### physics

Two dimensions. In the figure, three point particles are fixed in place in an xy plane. Particle A has mass mA = 4 g, particle B has mass 2.00mA, and particle C has mass 3.00mA. A fourth particle D, with mass 4.00mA, is to be

asked by fadi on April 8, 2017
5. ### Physics

Three particles X, Y, and Z of masses 2 kg, 5 kg, and 4 kg respectively are arranged in order along a straight line. Y is 5.0 m from X and 7.0 m from Z. The distance of the centre of mass of the system of mass from X is? ANS: 6.6

asked by Ariana on November 1, 2014
6. ### Physics

Cn u xplain the solutions steps by steps? Cz i really dnt understand wen i revise it nw. Tnxs u kindly. Two particles A & B are connected by a light inextensible string passing over a smooth pulley P. Particle A, of mass m, lies

asked by Spirit on September 29, 2008
7. ### TO: MS SUE SCIENCE HELP

this question has really stumped me but i have tried doing it and have came up with some possible answers: the following letters list some characteristics OF SOLIDS ACCORDING TO THE KINECTIC MOLECULAR THEORY. A.) the particles are

asked by SPIKE on December 14, 2012
8. ### Physics

Two identical charged particles of mass m=1.6 kg and electric charge Q=-5.2 μC are placed on an frictionless 26° incline. One of them falls down to the bottom and stops against the wall. The other stays at rest in the middle of

asked by Alex on June 13, 2012
9. ### Physics

Three particles have identical masses and identical inital velocities. These particles are projected one at a time into a region in which there is a uniform magnetic field B perpendicular to their velocities. If two of the

asked by Andrea on April 21, 2008
10. ### Physics

Consider four masses arranged (clockwise from A at the top) in a cross (looks like a giant plus symbol). Each is 1cm from the center of the cross. Mass A has a charge +1𝜇C , mass B has a charge of −1𝜇C , and mass C has a

asked by Brett on July 28, 2019

More Similar Questions