Parts a-d (800) Problem 5: A dragster accelerates from rest down a track of leng
ID: 2031873 • Letter: P
Question
Parts a-d
(800) Problem 5: A dragster accelerates from rest down a track of length d= 400.0 m. In the absence of any friction the dragster has a constant acceleration of a 25 m/s2 in the direction of motion, and its mass is m-920 kg. Assume the dragster is moving in the positive horizontal direction. 25% Part (a) Assuming there is no rolling friction write an expression for the amount of net work done on the dragster. Wd-during the run, in terms of the given quantities Grade Summary Deductions Potential 0% 100% Submissions Attempts remaining:2 (0% per attempt) detailed view 12 3 Submit Hint I give up! Hints: 2% deduction per hint. Hints remaining: 2 Feedback: 2% deduction per feedback ? 25% Part (b) Now consider the existence of rolling friction which causes a total resistive force with magnitude F on the dragster. Write an expression for the work done by this force over a distance d 25% Part Give an expression for the total kinetic energy of the dragster. E in the presence of rolling friction after it travels a distance c d. 25% Part (d) What is the dragster's final speed. in meters per second, assuming F-1000 N?Explanation / Answer
A) Wd = force * distance = (m*a)*d = mad
B) friction work Wf = -Fr* d = -Frd
(You might not need the sign in your answer; Fr might be taken to be negative. )
C) By work-energy theorem,
KE = net work = Wd + Wf = (ma – Fr)*d
D)
From the result of (C):
KE = (ma – Fr)*d
=> ½ mv2 = (ma – Fr)*d
=> v =sqrt[( 2*(ma – Fr)*d)/m]
= sqrt[(2*(920*25 – 1000)*400/920]
= 138.32 m/s