Question
1) Tom Brady throws an incomplete pass at an initial speed of approximately 60 miles/hour (mph). When the ball, with mass m = 400 grams was released, it's initial velocity vector made an angle of approximately 45 degree with respect to the ground. Question: What are the x- and y-components of the linear momentum when the hail was released? a) px = py = 7.6 kg m/s; b) px = py = 19 kg m/s; c) px = py = -7.6 kg m/s; d) none of the above. 2) In the problem above, what is the magnitude of the change in the ball's momentum? a) 25 kg*m/s b) 72.3 kg*m/s c) 15.2 kg*m/s d) 18.4 kg8m/s 3) Which of the following gives the correct vector notation for the initial linear moment of the ball? a) P0 = (7.6 kg m/s) x + (7.6 kg m/s) y b) P0 = (19 kg m/s)x + (19 7.6 kg m/s)y c) P0 = (-7.6 kg m/s)x + (-7.6 kg m/s)y d) none of the above 4) Apparently, a flea of mass m = 6.0 mg, can jump straight up to a height of 0.44 m. Calculate its initial linear momentum as it leaves the ground. a) 10 kg*m/s; b) 3 x 10^-3 kg*m/s; c) 1 x 10^-2 m/s, t = 2 s; or d) 18 x 10^-3 kg*m/s.
Explanation / Answer
v = 60 mph = 26.8 m/s
Vx = 26.8*cos45 = 19 m/s
Vy = 26.8*sin45 = 19 m/s
1 ) Pox = Poy = m*vx = 7.6 kg m/s
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2) p1x = 7.6 kg m/s
P1y = -7.6 kg m/s
dPx = P1x - Pox = 0
dPy = P1y - Poy = 15.2 kg m/s
option C
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3) Po = (7.6kgm/s)x + (7.6 kg m/s)y
option A
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4) H = v^2/2g
v = sqrt(2*g*h) = 2.93 m/s
P = m*V = 0.006*3 = 18*10^-3 kg m/s
option D
