7. A block of mass 2.50 kg on a smooth horizontal surface is pushed against an i

Question

7. A block of mass 2.50 kg on a smooth horizontal surface is pushed against an initially relaxed spring that has a force constant k-310 N/m, compressing it 1.50 meters. What is the stored energy in the spring? 8. A block of mass 2.50 kg on a smooth horizontal surface is pushed against an initially relaxed spring until the spring has 3.22 J of stored energy. The mass is then released, what is its velocity when it leaves the spring? There is no friction. 9. A 5.2 kg ball is dropped from a height of 44.2 m above the ground. What is the ball's kinetic energy as it hits the ground?

Explanation / Answer

7) Energy stored in spring = 0.5Kx^2 =0.5*310*1.5*1.5= 348.75 J (ans)

8) Using energy conservation

0.5 mv^2 = 3.22 J

v= 1.6 m/sec (ans)

9) Using energy conservation

KE = mgh = 5.2*9.81*44.2 = 2254.73 J (ans)

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