This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: oldhomewk 13 PAPAGEORGE, MATT Due: Feb 17 2008, 10:00 pm 1 Question 1, chap 6, sect 3. part 1 of 4 10 points A curve in a road is banked. There is a car on the curve. The acceleration of gravity is 9 . 8 m / s 2 . 1 . 5 M g = . 1 3 31 What is the component of its weight paral lel to the incline? Correct answer: 7571 . 06 N (tolerance 1 %). Explanation: Let : M = 1500 kg , v c = 31 . 732 m / s , Part2 r = 171 m , = 31 , and = 0 . 13 . Consider the free body diagram for the car M g s i n N = M g c o s N  W bardbl M a bardbl  mg Solution: The car is on an incline that makes an angle with the horizontal direction so the component of its weight parallel to the incline is W bardbl = M g sin = (1500 kg)(9 . 8 m / s 2 ) sin31 = 7571 . 06 N . Question 2, chap 6, sect 3. part 2 of 4 10 points If the radius of curvature is 171 m, what is the ideal speed of the car such that it doesnt rely on friction to keep from sliding sideways? Correct answer: 31 . 732 m / s (tolerance 1 %). Explanation: Since there is no frictional force keeping the car from sliding sideways, W bardbl = M a bardbl M g sin = M v 2 c r cos v 2 c = g r sin cos v c = radicalbig g r tan = radicalBig (9 . 8 m / s 2 )(171 m) tan(31 ) = 31 . 732 m / s . Question 3, chap 6, sect 3. part 3 of 4 10 points The next curve that the car approaches also has a radius of curvature 171 m. It is banked at an angle of 30 . The ideal speed for this curve is v c (banked so that the car experiences no frictional force). The speed of the car v s as it rounds this curve is v s = 0 . 543 v c . If the mass of the car is 1500 kg, what is the magnitude of the frictional force needed to keep it from sliding sideways? Correct answer: 5182 . 86 N (tolerance 1 %). Explanation: For this curve there is a new v c since r is different and is different. The frictional force acts either up or down the incline W bardbl + f = M a bardbl = M v 2 r cos = (0 . 543) 2 M v 2 c r cos . oldhomewk 13 PAPAGEORGE, MATT Due: Feb 17 2008, 10:00 pm 2 But we know that at the ideal speed, f critical = 0 and M v 2 c r cos = W bardbl ....
View
Full
Document
 Spring '09
 KLEINMAN
 Physics, Acceleration, Gravity

Click to edit the document details