Problem Solving Sample Problem A woman pushing a 3.5kg cart with a force of 380N along a horizontal surface. The cart moves at around 4.8m What is the final speed of the cart assuming that it came from rest? Given: m = 3.5kg F = 380N d = 4.8m Solution: Find Work: W = Fd = (380N)(4.8m) = 1,824] Find the final velocity using the equation: 2W 2(1,8241) 3.5kg = 32.28m/s 171 Practice Problem The Flash is seen running after a train with a mass of 450,000kg moving at 62m/s?. A) Find how much force is acted on the train. B) Calculate the amount of work he needs to put up with to catch upProblem Solving Sample Problem 1. A spring can be compressed by a force of 62 N by 0.25m, a) Find the force constant of the spring. B) How much force is needed to compress the spring by 0.5m? c) What is the elastic potential energy if it is compressed by 0.8m. a. Solution b. C. Given Given Given F = 62N x = 0.25m k = 248 N/m x = 0.5m k = 248N/m x = 0.8m Formula: Formula Formula F F = kx k= - EPE = -kx' F = (248 N/m) (0.5m) 1 248N 62N F = 124 N k = im )(0.8m) 0.25m EPE = 99 2 J k=248 N/m Practice Problem 1. A spring for the catapult was compressed by a 83 N force to 0.99m. a) Find the force constant of the spring. B) How much force is needed to compress the spring by 2.21m? c) What is the elastic potential energy if it is compressed by 0.2.5mProblem Solving Sample Problem 1. What is the gravitational potential energy of a 8kg object that was lifted at 5m above ground? 2. Tim climbed a 5m long slide with an inclination of 400 from the ground. What is the potential energy of Tim if his mas is 85kg? 1. Solution 2. Solution Given Given m = 8kg h= 5m g=9.8 m/s? m = 85 kg L = 5m 0 = 400 g = 9.8m/$2 Formula Formula GPE = mgh h = Lsine GPE = (8kg) (9.8m/s?) (5m) h = (5m) (sin409) GPE = 392 J h=3.21m GPE = mgh GPE = (85kg) (9.8m/s?) (3.21m) GPE = 2.673.93 J Practice Problem 1. Find the gravitational potential energy of the 15kg sack elevated at 15m. 2. A 60kg box is transported to a truck using a 15m inclined wood with an angle of 350 from the pavement