84.1 The position, velocity and acceleration vectors in two dimensions ()The velocity: F=2t i+2-t dr v =2i-2t j Magnitude: V =2 v,=-2t V"x+v=2√ +t t=2n2=2√5=4.47ms The angle between velocity and x-axis 4 a= tan tan 2 84.1 The position, velocity, and acceleration vectors in two dimensions v=,=2i-2tj dνd2r T he magnitu 2 Direction of the acceleration6 (3)The velocity: 2 4 tan tan 1 1 − = = − − x y v v α The angle between velocity and x-axis: ( ) -1 2 2 2 2 2 2 2 5 4.47 m s 2 1 2 2 2 2 d d 2 2 = = = ⋅ = + = + = = − = = − = + − t v v v v t v v t i t j t r v r t i t j x y x y r r r r r r r Magnitude: §4.1 The position, velocity, and acceleration vectors in two dimensions ( ) j t r t v a i t j t r v r t i t j ˆ 2 d d d d ˆ 2 ˆ 2 d d ˆ 2 ˆ 2 2 2 2 = = = − = = − = + − r r r r r r (3)The acceleration: Direction of the acceleration: The magnitude: a = a = 2 r j ˆ − §4.1 The position, velocity, and acceleration vectors in two dimensions