Which Statements About Moving a Block Are True?

[sonutulsiani]

Homework Statement

A block of mass m is resting on a horizontal surface whose coefficient of static friction is μs.

http://bcs.whfreeman.com/WebPub/Physics/tiplerphysics6e_bridge/question_bank_images/fig5-65.png?2439

Which of the following statements (if any) are true?

A. If you want to apply the minimum possible force to move the block, you should apply it with the force pulling upward at an angle θmin = arctan μs.
B. The minimum force necessary to start the block moving is μs mg/ √1 + μs2.
C. Once the block starts moving, if you want to apply the least possible force to keep it moving, you should keep the angle at which you are pulling the same.

There may be more than 1 answer

Homework Equations

Fs=μs Fn

The Attempt at a Solution

No idea.

 

[tiny-tim]

Hi sonutulsiani!

Call the normal force N, and the friction force H.

Then do a vector triangle or x and y component equations for a fixed angle θ …

what do you get? ​