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Department of Natural Sciences Clayton State University February 18, 2014 Physics 2211 – Quiz 4 Name ______SOLUTION_______________________________ 1. A Honda Civic travels in a straight line along a road. Its distance x from a stop sign is given as a function of time t by the equation x(t)= α t2− β t3, where α = 1.52m/s2 and β = 4.75×10−2m/s3. a. V x , av b. V x , av c. Calculate the average velocity of the car for the time interval t = 0 to t1 = 1.93 s. x f xi t f ti 5.32 m 0 2.76 m / s 1.93 s Calculate the average velocity of the car for the time interval t = 0 to t2 = 4.05 s. x f xi t f ti 21.77 m 0 5.38 m / s 4.05 s Calculate the instantaneous velocities of the car at t1 = 1.93 s and t2 = 4.05 s. V x 2t 3t 2 Vx (t 1.93 s) 5.34 m / s Vx (t 4.05 s) 9.98 m / s d. a x , av Calculate the average acceleration of the car from t1 = 1.93 s to t2 = 4.05 s. Vx f Vx i t f ti 2.19 m / s 2 e. Calculate the instantaneous acceleration of the car at t1 = 1.93 s. a x 2 6t 2.49 m / s 2 2. The figure shows the velocity of a solar-powered car as a function of time. The driver accelerates from a stop sign, cruises for 20 s at a constant speed of 60 km/h, and then brakes to come to a stop 40 s after leaving the stop sign. a. Compute the average acceleration during the time interval t=0 to t=10s. V x (0) 0 V x (t 10 s) 60 km / h 16.7 m / s a x 1.67 m / s 2 b. What is the instantaneous acceleration at t=20s? Zero