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Name ____________________ Class ______ Homework — Combined Forces General strategy:! ! 1. Carefully read question! 2. Draw diagram — often a free body diagram is ! most helpful! 3. Write a list of variables for which you know the ! value! 4. Write a list of variables that you must find to solve ! the problem! 5 Gather any equations that you think might help! 6 Plug away, being careful to follow algebra rules ! and free body diagram rules Newton’s 2nd ! Hooke’s Law ! Friction ! Velocity ! Displacement ! F = ma F = -kX F = µk FN v = vo + at x = xo + vot + ½at2 Gravity on Earth g = 9.8 m/s2 ! ! 1. A car goes from 0 to 35 m/s in 7 seconds. If the force pushing the car is 5,600 N, what is the mass of the car? ! ! ! ! ! ! ! ! ! ! 2. A bowling ball is suspended from a spring (k=12 N/cm). If the spring is 35 cm before the ball is attached and 38 cm after the ball is attached, what is the mass of the ball? ! ! ! ! ! ! ! ! ! ! ! Name ____________________ Class ______ ! 3. A 7,200 N force is applied to a 650 kg car. ! a) What will be the car’s acceleration?! ! ! ! b) If the coefficient of friction is 0.55, what will be the car’s acceleration?! ! ! ! c) How long will it take for the car to reach 45 m/s?! ! ! ! d) How far will the car travel in that time?! ! ! ! e) How fast will the car be traveling after 15 seconds?! ! ! ! ! ! ! ! 4. A 55 g hockey puck is hit at 24 m/s. If the coefficient of friction between the puck and ! the ice is 0.080, how far will the puck travel before it stops?! ! ! ! ! ! ! * draw a free body diagram! * what is the net force on the puck?! * what is the acceleration (deceleration?) of the puck?! * how long will it take to go from 28 m/s to 0 m/s?! * how far will it travel?
