What is the Maximum Acceleration of a Towed Block on an Inclined Plane?

[Nazz_Designs]

Homework Statement

Two identical blocks A & B each of mass, m, are connected together by a light string, S₁, and are placed on a smooth plane inclined at 30degrees to the hotizontal. A second string, S₂, is attached to block A and is used to tow the blocks up the slope with S₂ inclined at 30degress to the slope.

a) Show that if block A is to remain in contact with the slope, the tension in S₂ cannot exceed mg.sqrt3 and hence find the maximum possible acceleration of the system.

b) Show that the ration between the tensions in S₁ and S₂ is sqrt3 : 4, independent of the acceleration of the system

Homework Equations

All the equation you may need to use

The Attempt at a Solution

Dont know where to start from. When the questions states if block A needs to remain in contact.. its confusing me.

 

[Delphi51]

The thing is that the string is at an angle to the slope and thus tends to lift block A off the slope. You'll have to find the normal force(s) and find the value of the string force that makes the total normal force zero (liftoff).

 

[Nazz_Designs]

i know the principle, i just can't come to prove it... if anyone can show me the first lines.

 

[Delphi51]

Can you find the component of mg that is normal - straight into the slope? Then do the same for the string force. If you can't see it, draw a diagram and show the forces separated into normal and parallel to the ramp components.