Question

A man drags a 71-kg crate across the floor at a constant velocity by pulling on a strap attached to the bottom of the crate. The crate is tilted 25° above the horizontal, and the strap is inclined 61° above the horizontal. The center of gravity of the crate coincides with its geometrical center, as indicated in the figure. Find the magnitude of the tension in the strap.

Answer 1

Answer:

T = 540 N   (to two significant digits)

Explanation:

Let the crate dimension L be from strap attachment to floor contact

Let T be the strap tension

sum moments about the floor contact point to zero

mg[½Lcos25] - Tsin61[Lcos25] + Tcos61[Lsin25] = 0

L is common to all terms, so divides out.

½(71)(9.8)cos25 = T(sin61cos25 - cos61sin25)

T = (71)(9.8)cos25 / (2(sin61cos25 - cos61sin25))

T = 536.428020...