2. You pull a 70 kg block up a 400 incline so that the tension of the rope is pa

Question

2. You pull a 70 kg block up a 400 incline so that the tension of the rope is parallel to the incline. The block starts from rest and the incline has a coefficient of friction of 0.4. The tension is such that the block accelerates up the ramp at 1.5 m/s2.
a. Draw a free body diagram.
b. What is the tension?
c. If the block moves 5 m, using kinematics, what is the final velocity?
d. How much work does each force do on the block while moving the 5 m?
e. What is the net work done on the block?
f. Using the work energy theorem, what is the final velocity of the block?
g. How long does it take you to pull the block 5 m (use kinematics)?
h. What is the impulse given the block for this time period? (hint: impulse is defined as a NET force for a short period of time).
i. What is the change in momentum across the 5 m? Are your answers consistent?

Explanation / Answer

accelaration = 1.5 c) so final velocity => V2 = 2*a*S => V=sqrt(2*1.5*5) = 3.873 m/s d) force of friction = mu*Mg*Cos(?) = 0.4*70*9.8*Cos(40) = 210 N work done by friction = 210*5 = 1051N work done by gravity = MgSin(?) * 5 = 2204 N tension force => T - (mu*Mg*Cos(?) + MgSin(?)) = 70*1.5 => T=756 N work done by tension force = F*5 = 3780 N e) net work = 3780-2204-1051 = 525N f)net work done = 1/2 MV2 = 525 N => V=3.87m/s g)time = sqrt(2*S/a) = 2.581 s h) impulse = change in momentum/time = M*3.87/2.581 = 105 N/s i)change in momentum = impulse * time = 105*2.581 = 270.9 change in momentum = MV =>V = 270.9/70 = 3.87 m/s so they are consistent

Related Questions

Navigate

• Browse (All)
• Browse 2
• Subjects

---

---

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