7. [-/1.53 Points] DETAILS SCALCET9 6.4.009.EP. MY NOTES ASK YOUR TEACHER PRACTICE ANOTH According to Hooke's Law, the force required to hold the spring stretched x m beyond its natural length is given by f(x) = kx, where k is the spring constant. Suppose that 3 J of work is needed to stretch a spring from its natural length of 26 cm to a length of 40 cm. Find the exact value of k, in N/m. k = N/m (a) How much work (in ]) is needed to stretch the spring from 30 cm to 32 cm? (Round your answer to two decimal places.) (b) How far beyond its natural length (in cm) will a force of 35 N keep the spring stretched? (Round your answer one decimal place.) cm Need Help? Read It Watch It Submit Answer 8. [-/1.53 Points] DETAILS SCALCET9 6.4.012.EP. MY NOTES ASK YOUR TEACHER PRACTICE ANOTH According to Hooke's Law, the force required to hold the spring stretched x m beyond its natural length is given by f(x) = kx, where k is the spring constant. Suppose that 12 J of work is needed to stretch a spring from 10 cm to 14 cm and another 20 J is needed to stretch it from 14 cm to 18 cm. Find the exact value of k, in N/m. K = N/m What is the natural length of the spring, in cm? cm Need Help? Read It1. [-/1.53 Points] DETAILS SCALCET9 6.4.AE.001. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Example 1 Video Example () (a) How much work is done in lifting a 1.5-kg book off the floor to put it on a desk that is 0.6 m high? Use the fact that the acceleration due to gravity is g = 9.8 m/s. (b) How much work is done in lifting a 15-lb weight 7 ft off the ground? Solution (a) The force exerted is equal and opposite to that exerted by gravity, so the force is F = m- d's dt 2 = mg = (1.5)(9.8) = N and then the work done is W = Fd = 1(0.6) = (b) Here the force is given as F = 15 lb, so the work done is Screen capture . now W = Fd = 15 . 7 = ft - lb . Screenshot taken Notice that in part (b), unlike part (a), we did not have to multiply by g because we were given the weight (which is a force) and not the mass of the object. Show in folder Need Help? Read It