*12.  A golf ball strikes a hard, smooth floor at an angle of 30.0° and, as the drawing shows, rebounds at the same angle. The mass of the ball is 0.047 kg, and its speed is 45 m/s just before and after striking the floor. What is the magnitude of the impulse applied to the golf ball by the floor? (Hint: Note that only the vertical component of the ball’s momentum changes during impact with the floor, and ignore the weight of the ball.)

 

Look at momentum before and after

Let’s make up as + and down as -.  Since there are no forces acting in the x direction the momentum in the x direction is not changed.  But there is a force in the up y direction so the y momentum is changed.  Since the x component does not change and the angle does not change the y component must be the same in magnitude.  The impulse-momentum theorem provides 

 

 

 

From diagram we can see

and

 

 

 

 

 

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This page last updated on January 11, 2020