6. A small puck is sliding along a frictionless surface. The puck hits a spring

Question

6. A small puck is sliding along a frictionless surface. The puck hits a spring (firmly attached to a wall) and rebounds with the same speed, but in the opposite direction. Which of the following statements is true regarding the puck? a) The energy of the puck is conserved. b) The momentum of the puck is conserved. c) Both the energy and momentum of the puck are conserved. d) Neither the energy, nor the momentum of the puck are conserved. e) It is impossible to tell without the initial speed and mass. 7. The figures below show systems containing a block attached to the end of a spring resting on a frictionless surface. In each system, the springs are stretched by a student to the right by a distance given in the figure. The mass and for constant are also given for each system. Which mass has the most potential energy?

Explanation / Answer

6. a) energy is conserved.

(because speed and mass same initially so energy = mv^2 /2 )

( in case of momentum, direction of momentum is changed , momentum is vector quantity)

7. p.E> = kx^2 /2   

for A = 5 x 0.4^2 /2 = 0.4 J

B = 5 x 0.2^2 /2 = 0.1 J

c . 4 x 0.2^2 /2 = 0.08 J

d 1 x 0.5^2 /2 =0.125J

e. 4 x 0.5^2 /2 = 0.50 J

f . 1x 0.5^2 /2 = 0.125 J

so its max. in E. ----------Ans

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