Acceleration of mass?

[Honk]

Hi Folks.

Is there any physicist hanging around here that can help me answer a question.

If I have a force of 135lbs pushing against a 39lb weight along a straight line without friction.
How fast will the weight accelerate at the first foot of length?
And what is the speed of the weight one foot away from the starting point?

Hopefully can any of you clever guys help me calculate this.

/ Honk

[mikestocks2006]

Hi Folks.
...If I have a force of 135lbs pushing against a 39lb weight along a straight line without friction.
How fast will the weight accelerate at the first foot of length?
And what is the speed of the weight one foot away from the starting point?...

/ Honk

Hi Honk,
At the end of the first foot, linear force application, linear motion, perpendicular to the force of gravity vector at that point, and starting with zero speed:

time to travel the first foot about 0.13 sec

speed about 14.9 ft/sec

I hope this helps.

ps: good work on the controler for the Hilden Brandt motor.

[Honk]

Thank you for your input.

I did some calculations but I could not verify them myself.

I converted the 135lbs force to Nm and got 183Nm.
And I converted the mass from 39lb to 17.7kg
Then I divided the 183Nm by 17.7kg and got 10.33.
I have read that this number is the acceleration at meters/sec in square.

Earth gravity = 9.81 m/s?
My mass = 10.33 m/s?

If I'm right here I should have better acceleration than the gravity of Earth?
According to your calculations the mass should have reached 16.6km/h (10.31mph) when traveled one foot.

Queston: How did you calculate 14.9 ft/sec (4.47m/sec) at one foot away?

[mikestocks2006]

Thank you for your input.

I did some calculations but I could not verify them myself.

I converted the 135lbs force to Nm and got 183Nm.
And I converted the mass from 39lb to 17.7kg
Then I divided the 183Nm by 17.7kg and got 10.33.
I have read that this number is the acceleration at meters/sec in square.

Earth gravity = 9.81 m/s?
My mass = 10.33 m/s?

If I'm right here I should have better acceleration than the gravity of Earth?
According to your calculations the mass should have reached 16.6km/h (10.31mph) when traveled one foot.

Queston: How did you calculate 14.9 ft/sec (4.47m/sec) at one foot away?

Hi Honk,
I stayed within the British system of units to keep it simple, but the results are the same if converted to SI and back to British to get speed in ft/sec

With 135 lbs force and a body weighing 39 lbs
Your acceleration is about 3.4 times the acceleration of gravity
About 111.4 ft/(sec^2)
Or
About 33.9 m/(sec^2)

The unit conversions you?ve used are not applicable. (easy mixup for many)
For example from British to SI
1lb (force) equals 4.448 Newton  etc
So the 135 lbs (force) equals about 600 Newtons.

As for the weight of 39 lbs, it needs to be converted to mass, either Slugs in British unit mass, or Kgs (kilograms) unit mass in SI
So a body that weighs 39 lbs has a mass of  about 1.21 slugs (British units)
Or about 17.7 Kgs (SI units)

As for speed and time:

With constant force and constant mass, linear motion (path), linear force application, and again perpendicular to the force of gravity vector at that point, to be more precise (for the extend of the path traveled)

The formulas are
time to travel any given distance from zero start
t=sqrt(2x/a)
and speed at any given distance from zero start
v=sqrt(2ax)
where t=time, x=distance, a=acceleration


I hope this helps

[Honk]

Aha...I see where I made the errors.

I used this this torque convertor: http://www.gordonengland.co.uk/conversion/torque.htm  (TORQUE UNIT CONVERSION CALCULATOR)
but I should have used this one: http://www.gordonengland.co.uk/conversion/force.htm     (FORCE UNIT CONVERSION CALCULATOR)

Converting a force of 135lbs equals 600.51 Newton.
But I'm not sure whether the force acting on the 39lb weight is torque or force.

Perhaps I should clarify the problem.
I have calculated approx 135 foot pounds (ft-lbs) of stall torque in the motor I'm building.
Is this value to be seen as torque or force acting on the 39lb rotor?