# To find time

1. Jul 16, 2005

### Serj

I want to know how to find the time it takes for a mass to reach a velocity if a force is applied to it.

Last edited: Jul 16, 2005
2. Jul 16, 2005

### Staff: Mentor

One way is to apply Newton's 2nd law to find the acceleration, then integrate--or apply kinematic equations--to find the time: $v_f = v_i + a t$.

Another (equivalent) way is to use the "impulse-momentum" theorem: $F \Delta t = m \Delta v$.

3. Jul 16, 2005

### Serj

i'm terrible at math, can you isolate time on one side of the equation?

4. Jul 17, 2005

### HallsofIvy

What equation are you using?

5. Jul 17, 2005

### Serj

Vf=Vi + at

6. Jul 17, 2005

### ZapperZ

Staff Emeritus
Note that there is no mention of a constant force being applied here.

Zz.

7. Jul 17, 2005

### cscott

$$t = \frac{v_f - v_i}{a}$$

Make note of what ZapperZ said, though.

8. Jul 17, 2005

### Gokul43201

Staff Emeritus
cscott has done this for you, but you won't get very far with physics if you don't first brush up on elementary algebra. I strongly recommend you learn the math first.