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Homework Statement
A 12kg shopping cart rolls due south at 1.5m/s. After striking the bumper of a car, it travels at 0.80m/s at 30. degrees E of South. What is the magnitude and direction of the change in momentum sustained by the shopping cart?
Homework Equations
p = mv
The Attempt at a Solution
initial py = mv = 12kg * 1.5m/s = -18N
initial px = 0
final py = mv = 12kg * sin30 * 0.8m/s = -4.8N
final px = 12kg * cos30 * 0.8m/s = 8.31N
change in py = -4.8 + 18+ = 13.2N
change in px = 8.31N
magnitude of change in p = square root of (13.2N2 + 8.31N2) = 16N
angle of change in p = tan-1(13.2N/8.31N) = 58 degrees North of East
What am I doing wrong?