An object of mass m = 1.70 kg is travelling on a horizontal surface. The coeffic

Question

An object of mass m = 1.70 kg is travelling on a horizontal surface. The coefficient of kinetic friction between the object and the surface is muk = 0.200. The object has speed v = 1 .35 m/s when it reaches x = 0 and encounters a spring. The object compresses the spring a distance d/2, stops instantaneously, and then travels back to x = 0 where it stops completely. Eventually you will be asked to find the spring constant, k. 5. [1pt] Select all the statements that are true. E.g.. enter AB. You only have 5 tries! A. Friction is a non-conservative force. B. x= 0 is an equilibrium position where the spring exerts no force on the object. C. When the object comes to an instantaneous stop at x=d/2, its kinetic energy is zero. D. The work done by friction is equal to -mgmuk d, where d is the distance the object has travelled in contact with the spring. E. When the object reaches x=0 the second time, all its initial energy has gone into the compression and extension of the spring. F. KE+Espring = KE1 + Wfriction , where KE is the kinetic energy of the object at position x,Espring is the energy stored in the compressed spring at position x, KEi is the initial kinetic energy of the object when it first contacted the spring at x=0, and Wfriction is the work done by friction during the motion from x=0 to the position x.

Explanation / Answer

A: True

Forces that do not store energy are called nonconservative.

B: False

The object is travalling towards the spring

C: True

There no moment so v=0 ,so KE = 0 ( KE = m*v ^2 /2)

D:True

Work = Force * Distance

here Friction = - mg * u

and Distance = d

E: False

All energy has gone to work against the friction. Spring only store and release the energy.

F:True

Initial energy = KEi

Work done by Friction = Wfriction

Final energy = Initial energy + Work done                             ( mv^2/2 - mgux)

                    = energy in mass + energy in Spring = KE + Espring

Answer : ACDF

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