# Need Physics help pls

• Nov 7th 2012, 11:55 AM
Louisana1
Need Physics help pls
If a 75-kg sprinter can accelerate from 0.3 m/s to a speed of 10 m/s in 2 s, what average power is generated?

a. What is the Change in Kinetic Energy of the sprinter?
b. What is the WORK DONE by the sprinter?
c. How much power is does the sprinter generate during this process?

Need help with these equation
• Nov 7th 2012, 12:01 PM
MarkFL
Re: Need Physics help pls
a) $\displaystyle \Delta K=K_f-K_i=\frac{1}{2}m\left(v_f^2-v_i^2 \right)$

b) Use the work-energy theorem.

c) Power is the time rate of work.
• Nov 7th 2012, 12:02 PM
fkf
Re: Need Physics help pls
Quote:

Originally Posted by Louisana1
If a 75-kg sprinter can accelerate from 0.3 m/s to a speed of 10 m/s in 2 s, what average power is generated?

a. What is the Change in Kinetic Energy of the sprinter?
b. What is the WORK DONE by the sprinter?
c. How much power is does the sprinter generate during this process?

Need help with these equation

The unit of power is Watt (Joule/second).

The initial kinetic energy is
E_ki = mv^2/2 => E_ki = 75*0.3^2/2

The final kinetic energy is
E_kf = mv^2/2 => E_kf = 75*10^2/2

The change in kinetic energy is then
E_kf-E_ki = ...

The work done by the sprinter is the same as the energy turnover (is that correct English?)

We then have that the sprinter generates a power equal to the difference in kinetic energy over a period of time, in this case 2 seconds.
• Nov 7th 2012, 12:04 PM
HallsofIvy
Re: Need Physics help pls
Exactly what kind of help do you need? Apparently you are taking a course in physics involving kinetic energy. If so you should know that the kinetic energy of a body of mass m, at speed v, is (1/2)mv^2. Okay, you are given the mass and initial and final speed so what were the initial and final kinetic energies? Since "work" increases energy, the amount of work done is the change in energy. And "average power" is work done divided by the time it took to do the work.
• Nov 9th 2012, 12:48 AM
MarkFL
Re: Need Physics help pls
You should post your question in a new topic, and give the complete problem.

edit: never mind...I now see you are only here to pollute our forum with spam.