I need help with this LONG problem. I\'m lost and confused... (1)Three friends o

Question

I need help with this LONG problem. I'm lost and confused... (1)Three friends on Spring Break, Julia, Elena, and Ashley are pulling their car that broke down on the side of the road. The car is initially facing North. If Ashley pushes from behind with 300 N (in the direction the car is facing) and Elena pulls from the front 30 degrees west of North with a force of450N with what force must Julia pull the car shes pulling in a direction 45 degrees East of Due North if the car moves only North (No motion in the East-West direction)? If the car weighs 5000 N what is it's mass and acceleration? (2) If the car moves at the initial acceleration solved for in the last problem what happens if all three friends fall and let go of the car assuming the car is moving at 5 m/s when they fall? How long does the car take to come to a complete stop? What is the velocity at half of that time?

Explanation / Answer

F1 = 300 j

F2 = -450*sin30 i + 450*cos30 j

F3 = F*cos45i + F*sin45 j

Fnet = F1 + F2 + F3

Fnet is alon north(j)

Fnet = 300j - 450*sin30 i + 450*cos30 j + F*cos45i + F*sin45 j

- 450*sin30 i + F*cos45i = 0

F = 318 N

F3 = 318 N

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mass of the car = M = W/g = 5000/10 = 500 kg

acceleartaion a = Fnet /m

Fnet = 300j - 450*sin30 i + 450*cos30 j + 318*cos45i + 318*sin45 j

Fnet = 300j + 450*cos30 j + 318*sin45 - 450*sin30 i + 318*cos45i

Fnet = 914.5 N

acceleration = Fnet/m = 914.5/500 = 1.83 m/s^2 <<<-------answer

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3)

v = at = F/m)*t

v = (450*cos30 j + 450*sin30)/500*10

v = 7.8 j + 4.5 i

speed = sqrt(7.8^2+4.5^2) = 9 m/s

direction = 60 degrees east of north

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4)

distance x = v*t = 90 m

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