A 2.0-kg ball moving eastward at 3.0 m/s suddenly collides with and sticks to a

Question

A 2.0-kg ball moving eastward at 3.0 m/s suddenly collides with and sticks to a 4.0-kg ball moving northward at 2.0 m/s. What is the magnitude of the momentum of this ball system just after the collision? A. 14 kg middot m/s B. 2.0 kg middot m/s C. 10 kg middot m/s D. 6.0 kg middot m/s E. 8.0 kg middot m/s A machinist turns on the power to a grinding wheel at time t = 0 s. The wheel accelerates uniformly from rest for 10 s and reaches the operating angular speed of 58 rad/s. The wheel is run at that angular velocity for 30 s. and then power is shut off. The wheel slows down uniform at 1.4 rad/s^2 until the wheel stops. What is the total number of revolutions made by the wheel, starting from t = 0 s, till it finally stops?

Explanation / Answer

6. for ball,

vBi = 3 m/s i

for Stick,

vSi = 2 m/s j

momentum = m v

momentum of system = 2 x 3 i + 4 x 2j = 6i + 8j

from momentum conservation for collision,

initial = final momentum

Pf = 6i + 8j

magnitude = sqrt(6^2 + 8^2) =10 kg m /s

Ans(C)

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