Solving Work & Energy Problems: Homework Help

AI Thread Summary
A user seeks help with a physics problem involving a truck's deceleration and energy loss due to friction. The truck, weighing 9000 kg and traveling at 18 m/s, comes to a stop in 6 seconds, prompting calculations for distance traveled, acceleration, and energy loss. Initial attempts involve using Newton's laws to find acceleration and distance, but the user struggles with calculating energy loss. Another participant suggests using the change in kinetic energy to determine the energy lost, aligning with the conservation of energy principle. The discussion emphasizes applying both energy concepts and Newton's laws to solve the problem effectively.
Chris18
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Homework Statement


Hey guys. I have a problem to solve but I am stacked and I don't now how,so any help will be hghly appreciated.The problem is the following: A truck of mass 9000kg is moving with speed 18m/s, when the driver decides to stop and applies the brakes. After 6s the truck stops. Assuming that the stopping is with constant deceleration calculate the followin:

a)The distance traveled by the car during stopping
b)The acceleration of the truck
c)The loss of energy due to friction

I would be grateful if you can give me some ideas using energy mostly but I wouldn't mind if you tell me another way through Newton Laws e.t.c!

Homework Equations

The Attempt at a Solution


So I personally started (a) by finding the acceleration through Newton's Second law a=F/m...Then I used v^2/2a to define the distance traveled (S)...So i found the acceleration in question (a) so (b) is ready as well i think..I don't know what to do in (c) though
 
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d = -(speed)^2/(2*deceleration)
is the minimum distance travelled
 
Tell us what you know about how work is calculated, and about the work-energy theorem.

Chet
 
Well work is calculated by W=F*d*cos(θ). I know the basics of the work-energy theorem. Still I can't understand how to solve part (c) of the problem...
 
Chris18 said:
Well work is calculated by W=F*d*cos(θ). I know the basics of the work-energy theorem. Still I can't understand how to solve part (c) of the problem...
What is the change in kinetic energy of the truck?

Chet
 
My idea is to use the equation of kinetic energy since the loss of energy must be equal to the initial kinetic energy of the truck according to law of conservation! Tell me if I am wrong pls! Best regards.
 

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