Calculating Work Needed to Stop a 1000kg Car at 100km/h

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In summary, the conversation discusses the problem of finding the amount of work needed to stop a 1000kg car traveling at 100km/h. The individual suggests converting the speed to m/s and using the standard formula for energy to solve the problem. The final answer is 3.858 x 10^5 J.
  • #1
dzem68
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This should be easy...the problem asks for the amount of work needed to stop a 1000kg car traveling @ 100km/h.

I am having a hard time do to the fact acceleration,distance nor time is given.

here is how I think i need to approach this:

convert 1000km/h to m/sec

find acceleration

use Work=Mas*acceleration*Distance to find work

Here are the variables i know:

Mas=100kg
Vf = 0
V0 = 27.78 m/s

how can i find acceleration if no distance or time is given? I would think i need to find acceleration to calculate work needed to stop.

any hints?:smile:

dz
 
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  • #2
Originally posted by dzem68
the problem asks for the amount of work needed to stop a 1000kg car traveling @ 100km/h.


convert speed to m/s:
100km/h * 1000m/km * h/3600s = 27.7777m/s

you have to remember the standard formula for all of these types of problems is energy in = energy out. expanded, it looks like this:
Wo + Ko + Po = Wf + Kf + Pf

W is work, K is kinetic energy, P is potential energy. For this equation, there is no work put in, no initial potential energy, no final potential energy, no final kinetic energy. With all the 0 terms removed, it looks like this:
Ko = Wf

solfing for equation:
(1/2)mv^2 = W
(1/2)(1000)(27.777^2) = W
W = 385800J
W = 3.858 x 10^5 J
 
  • #3
In order to stop any object, you need to reduce its velocity to 0. That means you need to reduce its kinetic energy to 0. Work is energy so: calculate the kinetic energy. That's the work you need to do to stop the object.
 

1. How is work defined in physics?

In physics, work is defined as the product of the force applied on an object and the displacement of the object in the direction of the force.

2. What is the formula for calculating work?

The formula for calculating work is W = F x d, where W is work, F is the force applied, and d is the displacement of the object.

3. How do you calculate the force needed to stop a 1000kg car at 100km/h?

To calculate the force needed to stop a 1000kg car at 100km/h, we use the formula F = ma, where F is the force, m is the mass of the car, and a is the acceleration (which is the change in velocity divided by the time). In this case, the acceleration is equal to the initial velocity (100km/h) divided by the time it takes to bring the car to a complete stop.

4. What is the displacement of the car in this scenario?

The displacement of the car in this scenario is the distance it travels while decelerating from 100km/h to a complete stop. This distance can be calculated using the formula d = (v^2 - u^2)/2a, where v is the final velocity (0km/h), u is the initial velocity (100km/h), and a is the acceleration.

5. How much work is needed to stop a 1000kg car at 100km/h?

To calculate the work needed to stop the car, we can use the formula W = F x d, where F is the force calculated in question 3 and d is the displacement calculated in question 4. Once we have these values, we can plug them into the formula and find the amount of work needed to stop the car.

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