15. An object of mass m = 8.10 kg is attached to an ideal spring and allowed to hang in the earth's gravitational field. The spring stretches 23.10 cm before it reaches its equilibrium position. The mass then undergoes simple harmonic motion with an amplitude of 10.5 cm. Calculate the velocity of the mass in m/s at a time t= 1.00s to three significant figures.

please solve and answer the question correctly. Thank you!!

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1. Some 1800 years ago Roman soldiers effectively used slings as deadly weapons. The length of these slings averaged about 81 cm and the lead shot that they used weighed about 30 grams. If in the wind up to a release, the shot rotated around the Roman slinger with a period of .14 seconds. Find the maximum acceleration of the shot before being released in m/s^2 and report it to two significant figures.

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11. A small charged plastic ball is vertically above another charged small ball in a frictionless test tube as shown in the figure.  The balls are in equilibrium at a distance d= 2.0 cm apart. If the charge on one ball is tripled, find the new equilibrium distance between the balls in cm and report it to the proper number of significant figures.

12. The electric field at a point 1.3 cm from a small object points toward the object with a strength of 180,000 N/C. Find the object's charge q, in nC to the proper number of significant figures. k = 1/4πε0 = 8.99 × 10^9 N ∙ m^2/C^2

14. When the potential difference between the plates of an ideal air-filled parallel plate capacitor is 35 V, the electric field between the plates has a strength of 670 V/m. If the plate area is 4.0 × 10^-2 m^2, what is the capacitance of this capacitor in pF? (ε0 = 8.85 × 10^-12 C^2/N ∙ m^2)

10. A small styrofoam ball of mass 0.500 g is placed in an electric field of 1140 N/C pointing downward.  What excess charge must be placed on the ball for it to remain suspended in the field?  Report your answer in micro-Coulombs to three significant figures.