# Energy recovered from a regenerative braking system

sanderalan
Homework Statement:
Energy recovered from a regenerative braking system. Where the maximum regenerative braking is 75% at 1.5g from 100 km/h for 0.5 seconds
Relevant Equations:
E = (1/2) * (m) * (delta v ^ 2)
Start velocity is 100 km/h, at 1.5g for 0.5 seconds the end velocity will be 73,52 km/h. So the energy can be calculated if the mass is present, but it is not given. Is there a way to calculate the regenerated energy with the given information?

Homework Helper
E = (1/2) * (m) * (delta v ^ 2)
Where did you get this equation?

Homework Helper
Gold Member
Maybe the OP meant delta (v^2).

• jbriggs444
Homework Helper
The equation is wrong. So let's look at that source to see whether you are misinterpreting it.

As I suspected, that equation does not appear on the page you reference.

• berkeman
sanderalan
The equation is wrong. So let's look at that source to see whether you are misinterpreting it.

As I suspected, that equation does not appear on the page you reference.
"The linear energy change is equal to:

Ke linear change =(1/2)mv1^2−(1/2)mv2^2"??

Please understand that I am working with limited information and this is what I found, Physics is not my expertise but I want to understand what I am missing in this problem...

Mentor
Homework Statement:: Energy recovered from a regenerative braking system. Where the maximum regenerative braking is 75% at 1.5g from 100 km/h for 0.5 seconds
Relevant Equations:: E = (1/2) * (m) * (delta v ^ 2)

So the energy can be calculated if the mass is present, but it is not given. Is there a way to calculate the regenerated energy with the given information?
The KE is definitely dependent on the mass. Is there more to the question?

Homework Helper
"The linear energy change is equal to:

Ke linear change =(1/2)mv1^2−(1/2)mv2^2"??
as @scottdave has noted, ##{v_1}^2 - {v_2}^2## is different from ##(v_1-v_2)^2##.

You were right to notice that kinetic energy depends on mass and that knowing the initial and final velocities does not help determine how much energy is gained or lost unless you also know the mass.

• berkeman
sanderalan
Thanks! Seems like the question was not complete in this case, as no mass was given