# Normal Force

What is the normal force of the incline on the block? (See attachment).

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#### Solution Summary

The solution for the calculation of the normal force given succinctly.

Basic Physics (Change of Momentum; Average Force Used; Average Angular Speed; Coefficient of Static Friction, etc ... )

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34. When bunting, a baseball player uses the bat to change both the speed and direction of the baseball. (a) Will the magnitude of the change in momentum of the baseball before and after the bunt be (1) greater than the magnitude of the of the momentum of the baseball either before or after the bunt, (2) equal to the difference between the magnitudes of momenta of the baseball before and after the bunt, or (3) equal to the sum of the magnitudes of momenta of the baseball before and after the bunt? Why? (b) The baseball has a mass of 0.16 kg; its speeds before and after the bunt are 15 m/s and 10 m/s, respectively; and the bunt lasts 0.025 s. What is the change in momentum of the baseball? (c) What is the average force on the ball by the bat?

54. Two identical cars hit each other and lock bumpers. In each of the following cases, what are the speeds of the cars immediately after coupling bumpers? (a) A car moving with a speed of 90 km/h approaches a stationary car; (b) two cars approach each other with speeds of 90 km/h and 120 km/h, respectively; (c) two cars travel in the same direction with speeds of 90 km/h and 120 km/h, respectively.

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72. A student investigating circular motion places a dime 10 cm from the center of a 33 1/3 -rpm record on a turntable. The record player can accelerate at 1.42 rad/s2. The student notes that the dime slides outward 2.25 s after she has switched on the turntable. (a) Why does the dime slide out-ward? (b) What is the coefficient of static friction between the dime and the record?

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(b) If a disk rotating at 800 rpm couples to a stationary disk with three times the moment of inertia, what is the angular speed of the combination?

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