A horizontal block-spring system with the block on a frictionless surface has total mechanical energy E = 55.2 J and a maximum displacement from equilibrium of 0.198 m.(a) What is the spring constant?Correct: Your answer is correct. N/m(b) What is the kinetic energy of the system at the equilibrium point?Correct: Your answer is correct. J(c) If the maximum speed of the block is 3.45 m/s, what is its mass?Correct: Your answer is correct. kg(d) What is the speed of the block when its displacement is 0.160 m?Correct: Your answer is correct. m/s(e) Find the kinetic energy of the block at x = 0.160 m.Incorrect: Your answer is incorrect.Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error. J(f) Find the potential energy stored in the spring when x = 0.160 m.Correct: Your answer is correct. J(g) Suppose the same system is released from rest at x = 0.198 m on a rough surface so that it loses 16.6 J by the time it reaches its first turning point (after passing equilibrium at x = 0). What is its position at that instant?

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Answer:

a) 2816.04 N/m b) 55.2 J c) 9.3 kg d) 2.03 m/s e) 19.15 J f) 36.05 J  g) 0.166 m

Explanation:

Total mechanical energy = 55.5 J, maximum displacement of the block (Xo) = 0.198 m

a) total energy = kinetic energy + potential energy where at maximum displacement the kinetic energy =0 since the body temporarily stop

55.2 = 1/2 K (Xo)² where Xo = 0.198 m

55.2 × 2 = K (0.198²)

K = (55.2 × 2) / (0.198²) = 2816.04 N/m

b) at the equilibrium position since the surface is frictionless  

Kinetic energy = total mechanical energy = 55.2 J

c) Kinetic energy = 1/2mVmax²

55.2 = 1/2m Vmax² where Vmax = 3.45 m/s

55.2 × 2 = m × (3.45²)

m = (55.2 × 2) / (3.45²) = 9.3 kg

d) total energy = kinetic energy + potential energy

total energy = 1/2mv² + 1/2K x² where v is the speed at 0.160m and x is the displacement from equilibrium point which = 0.16m

55.2 = 1/2×9.3 × v² + 1/2 × 2816.04 × (0.16²)

55.2 = 1/2×9.3v² + 36.05

55.2 - 36.05 = 1/2 × 9.3v²

19.15 × 2 / 9.3 = v²

v² = 4.12

v = √4.12 = 2.03 m/s

e) kinetic energy at 0.016m = 1/2 mv² = 1/2 ×9.3 × (2.03²) = 19.15 J

f) potential energy = 1/2 K x² = 1/2 × 2816.04 × (0.16²) = 36.05 J

g) total energy = 55.2 J at 0.198 m where kinetic energy at this point = 0 since the body was at maximum displacement from it equilibrium point

when the body was released its loss 16.6 to the first turning point after passing equilibrium at x = 0

at the turning point energy is conversed, kinetic energy at the point = 0

total energy = 55.2 - 16.6 energy loss to friction

total energy left = 38.6 = 1/2 × K × x1² ( unkown new maximum displacement)

38.6 × 2/ 2816.04 = x1²

x1² = 0.0274

x1 = √0.0274 = 0.166 m