Equilibrium and Elasticity problem hw due tomarrow

[brett812718]

[SOLVED] Equilibrium and Elasticity problem need help homework due tomarrow

Homework Statement

two identical, uniform, and frictionless spheres, each of weight W, rest in a rigid rectangular container. A line connecting their centers is at 45° to the horizontal.Find the magnitude of each of the following forces on the spheres in terms of W. (Hint: The force of one sphere on the other is directed along the center-center line.)
(a) the force from the bottom of the container
(b) the force from the left side of the container
(c) the force from the right side of the container
(d) the force from each other
here is a diagram of the spheres in the box
http://www.webassign.net/hrw/hrw7_12-59.gif

Homework Equations

Newtons second and third laws

The Attempt at a Solution

The contact force exerted by the lower sphere on the upper is along that is 45o and the forces exerted by the walls and floors are normal.

Equilibrium force on the top sphere leads to

Fwall = F cos 45 and F sin 45 = m g

According to Newtons third law the equilibrium of forces on the bottom sphere leads to

F'wall = F cos 45 and F'floor = F sin 45 +mg

a)magnitudes of the forces on the spheres from the bottom of the container

F'floor = mg +mg = 2mg
b)magnitudes of the forces on the spheres from the left side of the container

F'wall = mg
c))magnitudes of the forces on the spheres from the right side of the container

F'wall = mg
d) magnitudes of the forces on the spheres from each other

F = mg / sin 45 = mg * √2

but that is incorrect

 

[dynamicsolo]

When you say that the results are "incorrect", are you putting your answers into WebAssign? Don't forget that the weight of each sphere is called 'W', rather than being given as mg. So the machine either wants you to type answers like W, 1.414 W , and 2 W , or just the numbers 1, 1.414, and 2. (I get the same forces that you do.)

 

[brett812718]

yeah I entered the answers in terms of w but they were still wrong

 

[dynamicsolo]

yeah I entered the answers in terms of w but they were still wrong

Exactly what did you enter? The force analysis should be right, so we have to figure out just what WebAssign expects to see.

 

[brett812718]

I figured it out, I did not use a capital w in the answer. thanks for your time.

 

[dynamicsolo]

I figured it out, I did not use a capital w in the answer. thanks for your time.

WebAssign wouldn't take your answer because it's case-sensitive?!? Don'cha just lloooove computer-based problem systems?