HW 2 Begin Date: 9/7/2018 7:00:00 PM -- Due Date: 9/13/2018 11:59:00 PM End Date

Question

HW 2 Begin Date: 9/7/2018 7:00:00 PM -- Due Date: 9/13/2018 11:59:00 PM End Date: 12/31/2018 12:00:00 AM (10%) Problem 10: Two cars are heading towards one another. Car A is moving with an acceleration of ad = 11 m/s. Car B is moving with an acceleration of aB--11 m/s. The cars are initially at rest and separated by a distance d = 4700 m on the x-axis. 25% Part (a) At what time, in seconds. do the cars meet? Grade Summary 090 100% Potential sin0 cotan asin acos0 atan acotansinh) cosh tanh0 cotanhO cos0 Submissions Attempts remaining: 5 (500 per attempt) detailed view END Degrees ORadians BACKSPACE CLEAR Submit Hint I give up! Hints: 1 % deduction per hint. Hints remaining: 3 Feedback: 0%-deduction per feedback. 25% Part (b) What is the displacement. in meters, of Car A? 25% Part (c) What is the displacement. in meters, of Car B? 25% Part d Now assume that both cars start with an initial velocity. Car A's initial velocity is VOA 23 m/s and Car B s initial velocity is vB -47 m/s. At what time, t in seconds, do they meet?

Explanation / Answer

here,

aA = 11 m/s^2

for car B , aB = - 11 m/s^2

d = 4700 m

a)

let the time taken by cars to meet be t1

d = ( uA * t1 + 0.5 * aA * t1^2) - ( uB * t1 + 0.5 * aB * t1^2)

4700 = ( 0 + 0.5 * 11 * t1^2 ) - ( 0 - 0.5 * 11 * t1^2 )

solving for t1

t1 = 20.7 s

b)

the displacement of car A , sA = ( uA * t1 + 0.5 * aA * t1^2)

sA = ( 0 + 0.5 * 11 * 20.7^2 ) = 2356.7 m

c)

the displacement of car B , sB = s - sA = 2343.3 m

d)

intial speed of A , uA = 23 m/s

initial speed of B , uB = - 47 m/s

let the time taken by cars to meet be t2

d = ( uA * t2 + 0.5 * aA * t2^2) - ( uB * t2 + 0.5 * aB * t2^2)

4700 = ( 23 * t2 + 0.5 * 11 * t2^2 ) - ( - 47 * t2 - 0.5 * 11 * t2^2 )

solving for t2

t2 = 17.7 s

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