# Can one calculate velocity from force used?

1. May 21, 2015

### Q7heng

1. The problem statement, all variables and given/known data
This is a general problem, but if a 2kg object is given a push with a force of 20N, would one be able to calculate the velocity of the object if the surface is frictionless? Or does one need work and energy to find out the velocity?

2. Relevant equations
F=ma
Work=F delta distance
KE=1/2mv2

3. The attempt at a solution
I tried to find acceleration through that but wouldn't that be irrelevant on a frictionless track?

2. May 21, 2015

### haruspex

You posted equations showing that velocity can be determined from work done and mass, and that work done can be determined from force and distance force advanced.
You have quoted a mass and a force. What's missing if you want to determine the velocity?

3. May 21, 2015

### SteamKing

Staff Emeritus
Why would acceleration of the mass be irrelevant? The mass is starting out at zero velocity, so how does the velocity change?

Do you know the relationship between acceleration and velocity?

Do you know Newton's Laws of Motion?

4. May 22, 2015

### CWatters

If you know the starting velocity you can work out the final velocity as a function of time...

Definition of acceleration...

dv/dt = a

Integrate both sides.

v = at + constant

The constant is the starting velocity and gives you the equation of motion...

v = at + u ............................. (1)

F = ma
a = F/m .........................(2)

put (2) into (1)

v = Ft/m + u

I've omitted some assumptions.