If an object has position →rA as measured in a frame of reference xy that is moving at constant speed →v′B as measured in a second frame of reference x′y′, then in the \(x'...If an object has position →rA as measured in a frame of reference xy that is moving at constant speed →v′B as measured in a second frame of reference x′y′, then in the x′y′ reference frame: →r′A(t)=→v′Bt+→rA(t)→v′A(t)=→v′B+→vA(t)→a′A(t)=→aA(t) An acceleration can change the magnitude and/or the direction of the velocity vector.