- #1
waynexk8
- 398
- 1
Calculating force ?
I am trying to work out the force used on lifting a 91kg barbell for .5 of a second for 1.85M. And holding a 91kg barbell statically for 5 seconds.
Below is my attempt ?
To determine the force we will need to figure out what the weight of the barbell is (W = mg = 91 kg x 9.81 m/s² = 892 kg.m/s² or 892 Newtons).
Now, if work is equal to Force x distance then, U = 892 N x 1.85 m = 1650 Nm. 1 Newton meter “Nm” is equal to 1 joule, hence 1 joule is the work done when a force of 1 N moves through a distance of 1m in the same direction as the force.
As no distance is used on the static hold, the force used is 892N ?
The concept of power however, takes time into consideration. If for example, it took four seconds to complete the lift, then the power generated is 1650 J divided 4 s = 412.5 J/s. If on the other hand it only took 2 seconds to complete the lift, then the power generated is 1650 J divided 2 s = 825 J/s. Hence, the person who can lift the barbell in two seconds is more powerful than the one who lifted the barbell in four seconds.
So while the work done remains constant, more power is developed when mechanical work is done more quickly. Indeed, power can be thought of as how quickly or slowly work is done.
Thus for the person holding the barbell statically for 5 seconds we need to divided 892N by 5 = 178.4 Joules
However BY lifting the same 91kg for 1.85m in .5 of a second, first you x 892 N x 1.85 m = 1650 Nm, then divided 1650 by .5 = 3300 joules per second.
Wayne
I am trying to work out the force used on lifting a 91kg barbell for .5 of a second for 1.85M. And holding a 91kg barbell statically for 5 seconds.
Below is my attempt ?
To determine the force we will need to figure out what the weight of the barbell is (W = mg = 91 kg x 9.81 m/s² = 892 kg.m/s² or 892 Newtons).
Now, if work is equal to Force x distance then, U = 892 N x 1.85 m = 1650 Nm. 1 Newton meter “Nm” is equal to 1 joule, hence 1 joule is the work done when a force of 1 N moves through a distance of 1m in the same direction as the force.
As no distance is used on the static hold, the force used is 892N ?
The concept of power however, takes time into consideration. If for example, it took four seconds to complete the lift, then the power generated is 1650 J divided 4 s = 412.5 J/s. If on the other hand it only took 2 seconds to complete the lift, then the power generated is 1650 J divided 2 s = 825 J/s. Hence, the person who can lift the barbell in two seconds is more powerful than the one who lifted the barbell in four seconds.
So while the work done remains constant, more power is developed when mechanical work is done more quickly. Indeed, power can be thought of as how quickly or slowly work is done.
Thus for the person holding the barbell statically for 5 seconds we need to divided 892N by 5 = 178.4 Joules
However BY lifting the same 91kg for 1.85m in .5 of a second, first you x 892 N x 1.85 m = 1650 Nm, then divided 1650 by .5 = 3300 joules per second.
Wayne