53 4/5 3/5 4/3 Each numbered parts is worth 9 points. One extra point for FULL l

Question

53 4/5 3/5 4/3 Each numbered parts is worth 9 points. One extra point for FULL legible name at the top of page 5 An Olympic luge (sled) track has a vertical drop of 160 m and a length of 1600 m. A typical slider and her sled have a combined mass of 100 kg. Assume that she starts effectively from rest at the top of the track and reaches a final speed of 40 m/s (90 mph) at the bottom. 1. Find values for both the work done on her by gravity and the work done by non-conservative forces 2. Assuming the only non-conservative force that does work is sliding friction, find an average value for Ay. (Note that drag from the air is important at these speeds; but we are simply ignoring that),

Explanation / Answer

1. Work done by gravity = m g h

( h is vertical drop)

W_gravity = 100 x 10 x 160

= 160 x 10^3 J Or 160 kJ .......Ans

total work done = Work done by gravity + work done by conservative force = change in KE

160 x 10^3 + W = 100 ( 40^2 / 2 - 0 )

W = -80000 J or - 80 kJ ......Ans

2. W = F.d = F d cos(theta)

- 80000 = f (1600) cos(180)

f = 5/18 N

f = uk N = uk m g cos(phi)

sin(phi) = 160/1600

sin(phi) = 1/10  

cos(phi) = sqrt(99)/10

5/19 = uk (160 x10) sqrt(99)/10

uk = 1.75 x 10^-4

Related Questions

Navigate

• Browse (All)
• Browse 5
• Subjects

---

---

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