A 20-Kg Block Is Attached to One End of a Spring

question 88

Multiple Choice

A 2.0-kg block is attached to one end of a spring with a spring constant of 100 N/m and a 4.0-kg block is attached to the other end.The blocks are placed on a horizontal frictionless surface and set into motion.At one instant the 2.0-kg block is observed to be traveling to the right with a speed of 0.50 m/s and the 4.0-kg block is observed to be traveling to the left with a speed of 0.30 m/s.Since the only forces on the blocks are the force of gravity, the normal force of the surface, and the force of the spring, we conclude that:

• A)the spring is compressed at the time of the observation
• B)the spring is not compressed at the time of observation
• C)the motion was started with the masses at rest
• D)the motion was started with at least one of masses moving
• E)the motion was started by compressing the spring

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