Calculating acceleration and brake force

In summary, the question asks for the average force exerted by the brakes on a car of mass 600kg traveling at 45m/s and coming to rest in 12m. Using the equation Force = mass x acceleration, we can solve for acceleration by rearranging the equation v^2-u^2=2as to get a=(v^2-u^2)/2s. Plugging in the given values, we get an acceleration of 337.5 m/s^2.
  • #1
cyberhev
6
0

Homework Statement

Hi all, the question for revision is; A car of mass 600kg traveling at 45m/s comes to rest in 12m when the brakes are applied. What is the average force exerted by the brakes?

Homework Equations

Force = mass x acceleration V^2=u^2 +2as

The Attempt at a Solution

I know I need to work out the acceleration but am having trouble correctly transposing that equation I think its this v^2-u^2 divided by s =2a, its what to do with the 2 to get a on its own, does it then become 1/2 s on the other side?
 
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  • #2
cyberhev said:

Homework Statement

Hi all, the question for revision is; A car of mass 600kg traveling at 45m/s comes to rest in 12m when the brakes are applied. What is the average force exerted by the brakes?



Homework Equations

Force = mass x acceleration V^2=u^2 +2as



The Attempt at a Solution

I know I need to work out the acceleration but am having trouble correctly transposing that equation I think its this v^2-u^2 divided by s =2a, its what to do with the 2 to get a on its own, does it then become 1/2 s on the other side?

You're using the correct equation, but it looks like you need some help in "solving for a" to get the acceleration.

Let's write out what you correctly have so far:

[tex]
\frac{v^2-u^2}{s}=2a
[/tex]

Hopefully that helps you see better what to do ... if not, then post again.

p.s. I'm not quite sure if
1/2 s
means "(1/2)s" or 1/(2s).
 
  • #3
That is what i have so far, I am just not sure where the 2 goes so you just get a on its own, I was wondering the 2 then moves to the side of s to become1/2s.
 
  • #4
If I solve that equation with 2a. I did the following 45x45-0x0, divided by 12 = 168.75 x 2 =337.5. Is this the correct acceleration?
 
  • #5
[tex]\frac{v^2-u^2}{s}=2a[/tex]

[tex]\Rightarrow \frac{v^2-u^2}{2s}=a[/tex]
 
  • #6
Yes I have it, thank you, my transposition of equations knowledge is in there, but its 15 years or so since I used it! I often write the suvat list out, i find it very helpful.
 

What is acceleration?

Acceleration is the rate of change of an object's velocity over time. It is measured in units of distance per time squared, such as meters per second squared (m/s^2).

How do you calculate acceleration?

Acceleration can be calculated by dividing the change in velocity by the change in time. The formula for acceleration is a = (vf - vi) / t, where a is acceleration, vf is final velocity, vi is initial velocity, and t is time.

What is brake force?

Brake force is the amount of force applied by a vehicle's brakes to slow down or stop its motion. It is typically measured in units of newtons (N) or pounds (lbs).

How do you calculate brake force?

Brake force can be calculated by multiplying the coefficient of friction between the vehicle's tires and the road surface by the vehicle's weight. The formula for brake force is Fb = μ * W, where Fb is brake force, μ is coefficient of friction, and W is weight.

How are acceleration and brake force related?

Acceleration and brake force are inversely related. This means that as acceleration increases, brake force decreases, and vice versa. This is because acceleration is the change in velocity, while brake force is the force needed to slow down or stop the vehicle's motion.

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