Hello. I'm studying for my AP Physics C exam upcoming, so I'v e been doing practice problems out of this moderately difficult book. I ran into this question and wasn't too sure how to deal with it. Any hints or advice would be very much appreciated! "The displacement of an object of 1 kg mass as a function of time t in the x-y plane is given by [tex] x = 20t + 30t^2 [/tex] and [tex] y = 25 - 40t [/tex]. in the units of meters. The units of x and y are in meters and t is in seconds. The force acting on the object is?" The answer is 60 N in the constant x-direction. I initially thought [tex] F = dp/dt [/tex]. I figured that since I knew the mass, I could say [tex] F = m dv/dt [/tex]. To get the velocity, I figured I could find [tex] dx/dt [/tex] and [tex] dy/dt [/tex]. I wasn't too sure what to do then. I thought perhaps about finding the magnitude of the velocity, but wasn't too sure what to do. Any hints? Thank you. Edit: I think I may have figured it out. I realized that [tex] d^2x/dt^2 = 60 [/tex] and [tex] d^2y/dt^2 = 0 [/tex]. Thus, [tex] F = ma [/tex] and therefore, [tex] F = 60 N[/tex] in the x direction (as that is the only way it seems to be accelerating. Is my logic correct?