Practice Exam 2 - University Physics I | PHYS 2050, Exams of Physics

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PHYS 2050

Fall 2011 Exam # Instructions: answer all problems and show all relevant work needed to find solution. Draw diagrams/FBDs as necessary. Circle your final answer. Some (possibly) useful equations and constants v = v 0 + a t! ∆ x = v 0 t + ½ a t^2 v^2 = v 02 + 2a∆x a = a r + a t ac = v^2 /r g = 9.8 m/s^2 Σ F = m a! Ff = μkN! Ff = μsN ac = v^2 /r W = ΔK K = ½mv^2 W = F·d W = ∫ F· d r v^2 = v·v Problems:

1. (15 pts): Two blocks connected by a rope of negligible mass are being dragged by a horizontal force across a rough surface.. Each block experiences a different value of kinetic friction ( μK1 for block of mass m 1 and μK2 for block of mass m 2 ). Note: The acceleration of the blocks is unknown. (A) In terms of F, g , m 1 , m 2 , μK1 , and μK2 , find the tension, T between the blocks_._ (B) When the coefficients of kinetic friction are equal, what does the tension become?
2. (15 pts): While an elevator accelerates upwards, a person standing on a scale sees a scale reading of 1080 N. When the elevator slows down to a stop (same magnitude of acceleration), he sees a scale reading of 880 N. (A) What’s the rider’s mass? (B) What’s the magnitude of acceleration of the elevator?
3. (10 pts): A force F = (4x i + 3y j ) acts on a particle (4.00 kg) as it moves along the x-axis from the origin to x = 5.00 m. How much work is done on the particle?
4. Extra Credit (5 pts) : If the particle in #3 starts with a speed of 12.00 m/s, what is its speed at x = 5.00 m?