28. Melissa's favorite exercise equipment at the gym consists of various springs. In one exercise, she pulls a handle grip attached to the free end of a spring to 0.80 m from its unstrained position. The other end of the spring (spring constant = 45 N/m) is held in place by the equipment frame. What is the magnitude of the force that Melissa is applying to the handle grip? A) 29 N B) 36 N C) 42 N D) 54 N E) 66 N 29. When a force of 19 N is applied to a spring, it elongates 0.085 m. Determine the period of oscillation of a 4.0-kg object suspended from this spring. A) 0.8 s B) 1.2 s C) 3.1 s D) 4.1 s E) 6.3 s

A 4 kg object is released from rest from a height of 1.2 m above a vertical spring (initially in its natural state). The object strikes the top end of the spring compressing it at distance of 0.6 m. Find the spring's force constant.   A.) 261.33 N/m B.) 366.25 N/m C.) 480.00 N/m D.) 164.64

**14. A 15.0-kg block rests on a horizontal table and is attached to one endof a massless, horizontal spring. By pulling horizontally on the other endof the spring, someone causes the block to accelerate uniformly and reacha speed of 5.00 m/s in 0.500 s. In the process, the spring is stretched by0.200 m. The block is then pulled at a constant speed of 5.00 m/s, duringwhich time the spring is stretched by only 0.0500 m. Find (a) the springconstant of the spring and (b) the coeffi cient of kinetic friction betweenthe block and the table.

Do it quickly

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QUESTION 9 A 10-kg block is attached to one end of a horizontal spring on a level, frictionless surface. The other end of the spring is attached to a vertical support. The spring obeys Hooke's law and has a spring constant of k = 160 N/m. A physics student pulls the block outward so that the spring stretches by 40 cm. The student releases the block at time t = 0.00 s. Which of the following equations properly gives the position as a function of time? a. x(t) = (- 1.6 m/s)sin(4.0t) b. x(t) = (- 6.4 m/s2)cos(4.0t) C. x(t) = (10 m)cos(4.0t) d. x(t) = (0.40 m)cos(4.0t) e. x(t) = (4.0 m)cos(0.40t)

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