Required force to stop a moving object.

[aziiri]

Homework Statement

A solid object of 6kg was moving at a constant speed of 10m/s towards a man who try to stop it.
If the man stopped the train in 30 seconds, find the force F that the man exerted on the object.

The Attempt at a Solution

The only force acting on the object is the man's force so : ma=-F, this means that : v(t)=v(0)-F t /m.
We know that v(30)=0, which means that : F= m*v(0)/30 = 2.

Is my solution correct ? (I don't have anyone to ask him so I'm asking you).

 

[CAF123]

Homework Statement

A solid object of 6kg was moving at a constant speed of 10m/s towards a man who try to stop it.
If the man stopped the train in 30 seconds, find the force F that the man exerted on the object.

The Attempt at a Solution

The only force acting on the object is the man's force so : ma=-F, this means that : v(t)=v(0)-F t /m.
We know that v(30)=0, which means that : F= m*v(0)/30 = 2.

Is my solution correct ? (I don't have anyone to ask him so I'm asking you).

Seems fine, but put in units.

 

[ap123]

An alternative (and easier) way of doing this is to use the impulse-momentum theorem.