L=r x p r =<0-(-3),4-0,0>=<3,4,0> P= 1.5*<0,5,0> After the cross product, answer
ID: 1648580 • Letter: L
Question
L=r x p r =<0-(-3),4-0,0>=<3,4,0> P= 1.5*<0,5,0> After the cross product, answer should be (b) but real answer is c why? 7. [10 points] A ball of mass m 1.5 kg is falling straight down. At the instant shown, it is a height h 4.0 m above the floor and has a speed of 5 m/s. Consider point P at position i, =-30£ m, what is the angular momentum of the ball about point P? A. 0 2.5 2 kg m2 22.5 2 kg m2 4.om 5mIs. D. 152 kg m2 E. -15 2 kg m2 3 101 0 ~),o, v 37 tl The toraue about point Pexerted on the ball in the previousExplanation / Answer
In cross product, to know the direction of the resultant vector we use right-hand screw rule for cross product. In this, you have to point flat-handed ( right hand) in the direction of the first vector and bend the fingers into the direction of the second vector. If that's not easy you might have to rotate your wrist until it's possible. Then your thumb will be pointing in the direction of the product.
From above problem, point P is located on the negative x-axis, applying right-hand rule you can see that the resultant vector angular momentum is directed inside the page, that is, negative z-axis, thus a negative sign.
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