48% Fri 12:15 A ls Window Help s SCMA 2080 Assignment 3 2017 pdf (page 1 of 2) Q

Question

48% Fri 12:15 A ls Window Help s SCMA 2080 Assignment 3 2017 pdf (page 1 of 2) Q Search Instructions: Complete all questions on a separate piece of paper and submit at stort of class on Friday October 20th Show all work and include units where applicable Answer to 2 decimal places . A hammer thrower accelerates at a rate of 1.20 revs/s starting from rest. Determine a) how long 2. An ice skater increases his speed of rotation from 10 to 30 rad/s in a time of 1.2 s Determine his a) 3. Pilots and astronauts train to handle g-forces via large spinning centrifuges. If the arm of the and b) how many spins (revolutions) are required to reach an angular velocity of 1.90 revolutions per second angular acceleration, and b) angular displacement in this period. centrifuge is 12 m long, what must the constant angular velocity be to achieve the 9g's? A cyclist enters a slippery turn with a radius of 15 m travelling at 11 m/s. Determine the total 4. Acceleration experienc afrssibnt 3, an whether this is less than the acceleration that would be experienced if the cyclist just carried through the turn at the initial velocity BONUS: Determine the angle of the turn made after the 3 seconds of braking 5. Given the following diagram, if w 15 rad/s and the length of the shank is 52 cm determine the velocity (magnitude AND angle- will require some geometryl) of the ankle (A) relative to the knee (K). BONUS: If the knee is moving forward at a 8

Explanation / Answer

1. (A) alpha = 1.20 rev/s^2

wf = w0 + alpha t

1.90 = 0 + 1.20 t

t = 1.58 sec

(b) wf^2 - w0^2 = 2 alpha rev

1.90^2 - 0^2 =2 (1.20 ) rev

rev = 1.5 rev

2. (A) wf = w0 + alpha t

30 = 10 + 1.2 alpha

alpha = 16.7 rad/s^2

(b) wf^2 - w0^2 = 2 alpha theta

30^2 - 10^2 = 2(16.7) theta

theta = 24 rad  

3. a = w^2 r

9 x 9.8 = w^2 x 12

w = 2.71 rad/s

4. at = 1 m/s^2

v = 11 - 1x3 = 8 m/s

ar = v^2/ r = 4.27 m/s^2

a = sqrt(a_t^2 + a_r^2) = 4.38 m/s^2 .........Ans

for initial velocity. a_r = 11^2 / 15 = 8.07 m/s^2

so yes it is less than.

d = (11 x 3) - (1 x 3^2 / ) = 28.5 m  

theta = d / R = 1.9 rad ........Ans

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