Force in an instant, what's the time?

[albertlee]

If I throw a stone(1 kg) upwards and the intial velocity is 14m/s, And Does that mean the acceleration is (14m/s)/s ? and the force is 14N?

 

If so, how do i find out the time that I am exerting the force on the ball upwards? Secondly, I thought it must 1 second, because it never accelerates after intial volcity, and it is retarding due to the gravitational acceleration.....

 

So what is the time I am exerting force on the ball upwards?

 

Apreciate in advance

 

Albert

[J'Dona]

A change in velocity like would have to take a little time. The formula is:

 

 

Ft is the impulse. Since the mass starts at rest and u = 0, it's just Ft = mv. So Ft = 1 x 14 = 14 Newton seconds. There is a range of values that the force and time can take to give the same value of v; for example, a force of 14N over 1 second would give v = 14, or a force of 140N over 0.1 seconds would as well. You can find the acceleration in each case by rearraging F = ma, once you know the force.

[swansont]

A change in velocity like would have to take a little time. The formula is:

 

 

Ft is the impulse. Since the mass starts at rest and u = 0' date=' it's just Ft = mv. So Ft = 1 x 14 = 14 Newton seconds. There is a range of values that the force and time can take to give the same value of v; for example, a force of 14N over 1 second would give v = 14, or a force of 140N over 0.1 seconds would as well. You can find the acceleration in each case by rearraging F = ma, once you know the force.[/quote']

 

Note that that's the net force, not the force you are exerting, that tells you the acceleration (assuming you start at rest). And you are assuming the force is constant over the interval. If it's not you have to integrate.