# Solving Work & Energy Problems: Homework Help

• Chris18
In summary, the problem involves a truck of mass 9000kg moving at a speed of 18m/s and coming to a stop after 6s with constant deceleration. The three questions to be answered are: (a) the distance traveled during stopping, (b) the acceleration of the truck, and (c) the loss of energy due to friction. The solution involves using Newton's Second Law to find the acceleration, and then using the formula v^2/2a to calculate the distance traveled. For part (c), the work-energy theorem is used, with the change in kinetic energy of the truck being equal to the loss of energy due to friction.
Chris18

## 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!

## 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

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.

## What is work?

Work is defined as the amount of force applied to an object over a certain distance. It is measured in joules (J) and can be calculated by multiplying the force applied to an object by the distance it moves in the direction of the force.

## What is energy?

Energy is the ability to do work. It comes in many different forms, such as kinetic, potential, thermal, and chemical. Energy is measured in joules (J) and can be transferred from one object to another or transformed from one form to another.

## How do you calculate work?

To calculate work, you need to multiply the force applied to an object by the distance it moves in the direction of the force. The formula for work is W = Fd, where W is work in joules (J), F is force in newtons (N), and d is distance in meters (m).

## What is the conservation of energy?

The law of conservation of energy states that energy cannot be created or destroyed, but it can be transformed from one form to another. This means that the total amount of energy in a closed system remains constant.

## How do you solve work and energy problems?

To solve work and energy problems, you need to identify the type of energy involved (kinetic or potential), calculate the work done, and use the law of conservation of energy to determine the final energy state. It is important to accurately define the system and consider all forces acting on it to get the correct solution.

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