Two equal forces are to a door. The first force applied at the midpoint of the d

Question

Two equal forces are to a door. The first force applied at the midpoint of the door; the second force is applied to the doorknob near the edge of door. Both forces are applied perpendicular to the door. Which force exerts the greater torque? A. The first, at the midpoint B. The second, at the doorknob C. Both exert equal non-zero torques D. Both exert no torque. A fireman who is late to work is running towards the firehouse when one of the engines leaves, siren blaring, and accelerates toward her. Which describes she hears? A. sirens' pitch decreases and its amplitude decreases as it moves toward her. B. The sirens' pitch increases and its amplitude increases as it moves toward her. C. The sirens' pitch decreases and its amplitude increases as it moves toward her. D. The sirens' pitch increases and its amplitude decreases as it moves toward her. PART B: Free PICK 8 of the 13 Circle the PROBLEM NUMBER of the ones you want graded. If you complete more than 8, you will get partial credit for them as extra credit. A driver at a stoplight slams on the gas when the light turns green. The 4000kg car has a constant acceleration of 11m/s per second. a. How fast is the car moving after 2 seconds? b. How far has the car gone after 3 seconds? c. How far will the car have gone the moment the car reaches m/s? d. If he slams on the breaks when he reaches 44m/s and then stops bow much energy is lost?

Explanation / Answer

a) Using

v=u+at

v = 0 + 11*2 = 22m/s

b) Using

s = ut + 0.5at^2

s = 0*3 + 0.5*11*3^2 = 49.5m

c) Using

v^2 - u^2 = 2as

44^2 = 2*11*s

s = 88m

d) Energy lost = KE at 44m/s = 0.5mv^2 = 0.5*4000*44^2 = 3872000 J

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