Find MASS of a runner when work, power, and velocity are given?

In summary, the problem involves finding the mass of a runner who dissipates 0.35J of mechanical energy per step per kg of her body mass while running at a speed of 5m/s and developing a power of 75W. The equations for power and work are known, but the specific equation to find mass is unknown. By using the equation P = W/t and considering one step to be 1m, the work done can be determined. Then, by using the fact that the energy used is 0.35 J per kg, the mass can be solved for.
  • #1
kalisious
13
0

Homework Statement


While running in a cross country meet, a member of the team dissipates about 0.35J of mechanical energy per step per kg of her body mass. If she develops a power of 75W during the race and runs at a speed of 5m/s, find her mass.
PS: Consider one [of her] running steps to be 1m.


Homework Equations


I am unsure what equation to use to find mass. I know the equations to find power and work, but in relation to finding mass I am unsure.


The Attempt at a Solution


I cannot attempt a solution with no clue what equation to use to get me started.
I am able to do the work if I have proper equations.
Thanks!
 
Physics news on Phys.org
  • #2
Looks like the 75 Watts goes into making those steps.
P = W/t so you need to figure out the work done stepping over some convenient time. Maybe you could do it for one step?
 
  • #3
I am not sure what equation is used to find the mass though?
 
  • #4
It says the energy used is 0.35 J per kg. So the energy used is 0.35*m.
If you put that in the equation, you'll be able to solve for m.
 

1. How do you calculate the mass of a runner when given their work, power, and velocity?

To calculate the mass of a runner, you can use the formula: mass = work / (power * velocity). This formula is derived from the equation for power, which is work divided by time, and the equation for velocity, which is distance divided by time. By rearranging the equation, you can solve for mass.

2. Can the mass of a runner change during a race?

Technically, the mass of a runner can change during a race due to factors such as sweat loss or consuming fluids or food. However, these changes are usually negligible and can be ignored for the purpose of calculating the mass of a runner at a specific moment in time.

3. What units should be used for the inputs in the mass calculation formula?

The units used for work, power, and velocity should be consistent with each other. For example, if work is measured in joules, power should be measured in watts, and velocity should be measured in meters per second (m/s). It is important to use consistent units to ensure accurate calculations.

4. How does the mass of a runner affect their performance?

The mass of a runner can have a significant impact on their performance. Generally, a larger mass requires more work and power to move at the same velocity as a smaller mass. This means that a runner with a higher mass may have to exert more effort and expend more energy to maintain a certain pace, ultimately affecting their performance.

5. Can the mass of a runner be used to predict their speed or time in a race?

The mass of a runner is just one factor that can affect their speed and time in a race. Other important factors such as training, nutrition, and race strategy also play a role. While a lighter mass may generally result in a faster runner, it is not the sole determining factor and should not be solely relied upon for predicting race performance.

Similar threads

Finding the center of mass of a simple 2D shape
    • Introductory Physics Homework Help
Replies
9
Views
1K
Questions Regarding a Cat Going Up a Ramp
    • Introductory Physics Homework Help
2
Replies
56
Views
1K
Find the function of velocity of a person that accelerates to a constant v
    • Introductory Physics Homework Help
Replies
3
Views
813
What is the Work Done During a 100m Sprint?
    • Introductory Physics Homework Help
Replies
16
Views
2K
Find the power needed to accelerate this elevator downward
    • Introductory Physics Homework Help
Replies
4
Views
788
Shooting bullets, work & power
    • Introductory Physics Homework Help
Replies
26
Views
3K
Find tangential velocity given radius and the coefficient of friction
    • Introductory Physics Homework Help
Replies
3
Views
2K
Trouble solving for end state of two control volumes in a rigid tank
    • Introductory Physics Homework Help
Replies
12
Views
847
Calculating the mass of an object
    • Introductory Physics Homework Help
Replies
8
Views
1K
Finding the Mass of a Pole Vault Athlete
    • Introductory Physics Homework Help
Replies
7
Views
2K

Hot Threads

Recent Insights

Back
Top