Work, Energy, and Power Test Review

# Can you help him find the coefficient of friction ps

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The car comes to a stop over a distance of 50 m. Can you help him find the coefficient of friction? PS: He forgot the mass of the car and doesn’t know his mass either! µ=0.92 5) A ball is dropped from rest and it collides with a spring which brings it to rest over a distance of 0.15 m. The ball was originally 1.2 m above the spring whose constant is 350 Nm. What is the mass of the ball? 0.298 kg (BE CAREFUL ON THIS ONE WHERE YOU DEFINE H=0) 6) A mover uses a dolly (mass 8 kg) to move a large box (100 kg) up a 20 m long incline which is angled at 10° in 8 s. Assume box starts and ends at rest. a) How much work does the mover do? 3,675.8 J b) What is the change in gravitational potential energy? 3,675.8 J c) What is the mover’s power output? 459.5 W 7) How can you get the work done on an object by looking at a Force vs. Distance graph?

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8) A horizontal spring shoots a 3kg box along a horizontal frictionless surface. The box then goes up a hill inclined at 32º and the hill has a coefficient of kinetic friction of 0.3. The box travels 50m along the inline before stopping. If the spring constant for the spring is 780N/m, how far is the spring initially compressed? 1.72m 9) A 55kg person jumps in the air by applying a force of 2400N as they extend their legs a distance of 0.3m. How high will the person jump? (Ignore any changes in PEg while the legs are extending). 1.34m 10) Using the answer from the last problem assume the story starts at max height. How fast will they be going when they reach the ground if while they fall, air resistance does 500J of work? 2.84m/s 11) Using only work and energy to find the velocity of either mass after they have traveled 0.8 meters. THEN using old math reps, find the acceleration of the system. Your life would be easier if you assume initial velocity is zero. Also assume the pulley is frictionless and the sting is massless. 2.67 m/s, 4.46m/s 2 12) Find the velocity of the mass on the horizontal surface after it has traveled 0.4 meters. The coefficient of kinetic friction between the mass and the surface is 0.33. Assume masses start from rest. 2.24 m/s 13) How fast will the blocks be moving after the 2kg block slides 4m along the incline? 6.82m/s 25° 2kg 5kg 8kg 3kg 6 meters 8kg 3kg
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