The crate has a mass of 131kg and rests on a surface for which the coefficients

Question

The crate has a mass of 131kg and rests on a surface for which the coefficients of static and kinetic friction are = 0.3 and = 0.2, respectively.

If the motor M supplies a cable force of F = (8 + 20) N, where is in seconds, determine the power output developed by the motor when = 7s.

The crate has a mass of 131kg and rests on a surface for which the coefficients of static and kinetic friction are = 0.3 and = 0.2, respectively. If the motor M supplies a cable force of F = (8 + 20) N, where is in seconds, determine the power output developed by the motor when = 7s.

Explanation / Answer

F= 8 + 20t at max static friction force = 131*9.8*.3 = 385.3 N Tension in string when box starts moving = 385.3/3 = 128.38 N Time t at which box starts moving = (128.38-8)/20= 6.02 s Acceleration of box = [(8 +20 t)*3- 131*9.8*.2]/131 = (60t-236.76)/131 acceleration of calble= 3*(acceleration of box) = (180t-710.28)/131 at t= 7 s we get velocity by integrating acceleration w.r.t time from t = 6.02 s to t= 7 s we get velocity of cable = 3.454 m/s and force on cable = at t=7s = 148 N. so power = F.V = 148*3.454 = 511.2 W

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.