F=ma magnitudes only?

[horizon]

Hi,

Does F=ma only apply for MAGNITUDES?
For example, if F=4i-2j and mass is 2kg, would it be valid to say that 2a=4i-2j and a=2i-j, or should you always be working with the magnitudes of the forces (thereby giving a= root 5)?

Thanks in advance

[Bhootnike]

pretty certain its the vector - a = 2i - j.
unless it specifically asks for the magnitude of acceleration.

[Hancock]

F = ma applies for vector notation, but if you want to use magnitudes, you have to be consistent.

For example, (bold indicates vector)

F = ma
and
F = ma

but F =/= ma
and F =/= ma

[BigAl]

you resolute forces acting on the system.. for example a rocket accelerating upwards but following a track in the shape of parabola. For this case you will have net force..if you resolute that you will get horizontal and vertical components.you can use integration and differantation depending on what u need for upward force..and calculate time of flight and stuff. if there is just a force acting on horizantal there is upward force but in balance with weight..so u only have horizantal force..but normal force may change

[horizon]

thanks!