Unformatted text preview: the north. In unitvector notation, the velocity of P with respect to stationary guard A is v PA = 20cos θ 1 i + 20sin θ 1 j = 11.5 i + 16.4 j The velocity of B with respect to A is v BA = 30cos θ 2 i + 30sin θ 2 j = 27.2 i + 12.7 j The velocity of P relative to B is v PB = v PA – v BA = 15.7 i + 3.7 j The magnitude of v PB is v PB = √ ((15.7) 2 +3.7 2 ) = 16.1 m/s. The direction is θ = tan1 (3.7/(15.7)) = 13.3 + 180 = 167º, 13º north of west. Note that v PB has a negative x component and positive y component, so it is in the 2 nd quadrant. b) At that time, what are the magnitude and velocity of the acceleration of B relative to P ? Since P moves at a constant velocity, its acceleration is zero. Thus we have a BP = a BA – a PA = a BA It has a magnitude of 0.500 m/s 2 and is directed 25º north of east....
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 Summer '08
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 Acceleration, Work, Velocity, Vpb, guard A. Relative

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