Author Topic: How do I calculate velocity using force, mass and time?  (Read 1080 times)

I'm doing a science problem.
"Create a graph that shows the velocity of each cart each second for 10 seconds."
Here are my variables: mass1 = 50kg, mass2 = 70kg, force1 = 1000n, force2 = 1500n
I tried multiplying the mass by the force but that game me ridiculous answers like 150,000m/s which is not a speed you would get from a shopping cart.

I tried multiplying the mass by the force but that game me ridiculous answers like 150,000m/s which is not a speed you would get from a shopping cart.
When you multiplied your force by your mass, did you actually get 150,000m/s? Something about those units appears suspect.

When you multiplied your force by your mass, did you actually get 150,000m/s? Something about those units appears suspect.

70*1500=150,000 according to calculator.com

70*1500=150,000 according to calculator.com
No, the units. When you multiplied units of force with units of mass, did you actually end up with m/s?

No, the units. When you multiplied units of force with units of mass, did you actually end up with m/s?
I guess not.

F = M A
1000 = 50 A
1000/50 = A
A = 20

F = M A
1500 = 70 A
1500 / 70 = A
A = 150/7

V2 = V1 + A T

Looks like taking high school physics has finally played off for me :^)


Ah, i've figured something out.
It turns out mass times force is acceleration, so I will need to use acceleration to find my velocity.




velocity itself doesn't require energy and thus cannot be directly calculated using force and mass, that's inertia for you. acceleration is what needs energy

Ah, i've figured something out.
It turns out mass times force is acceleration, so I will need to use acceleration to find my velocity.
NO! Force = Mass * Acceleration, so Acceleration = Force / Mass!
I literally just did the calculations in my post :(

velocity itself doesn't require energy and thus cannot be directly calculated using force and mass, that's inertia for you. acceleration is what needs energy
That's an overly technical answer for a problem that almost certainly specifies both carts start at rest.

well, first you need to find the acceleration for both of them. you can do this by taking the F = ma equation and dividing both sides by the mass, so you end up getting F/m = a. Then just plug in the values: force1(1000N)/mass1(50kg) = 20 m/s^2 ; force2(1500N)/mass2(70kg) = ~21.43 m/s^2.

Then, use the vf = vi + at equation and plug in the values once more for each equation. i'm gonna assume that vi is 0.

vf = (20 m/s^2)(10 s)
vf = 200 m/s

vf = (21.43 m/s^2)(10 s)
vf = ~214.28 m/s

also protip: these numbers are ridiculous because friction and air resistance isn't taken into account. you will never see a shopping cart at roughly 447 miles per hour.
« Last Edit: December 03, 2015, 08:26:10 PM by Glass Joe »

also protip: these numbers are ridiculous because friction and air resistance isn't taken into account. you will never see a shopping cart at roughly 447 miles per hour.

well hey man, maybe he's doing the math  for how to do an orbital transfer with a shopping cart in space

Looks like taking high school physics has finally played off for me :^)

MA the F be with you