Question

A 330 kg box rests on an adjustable ramp having s = 0.25. The angle on

inclination of the ramp is increased until the box begins to slide. At what angle

will the box begin to slide?

Answer 1

Wb = M*g = 330 * 9.8 = 3234 N.

Fp = 3234*sin A = Force parallel to the
incline.

Fn = 3234*Cos A = Force perpendicular to
the incline.

Fs=u*Fn = 0.25 * 3234*Cos A = 809*Cos A = Force of static friction.

Fp-Fs = M*a.
3234*sin A-8o9*Cos A = M*0 = 0.
3234*sin A = 809*Cos A.
Divide both sides by Cos A:
3234*sin A/Cos A = 809.
sin A/Cos A = Tan A.
3234*Tan A = 809.
Tan A = 809/3234 = 0.25.
A = 14 Deg.