As Shown in the Figure, a 1 $v_ \mathrm { 1 } = 1.2 \mathrm {~m} / \mathrm { s }$

question 167

Multiple Choice

As shown in the figure, a 1.45-kg block is held in place against the spring by a 21-N horizontal external force. The external force is removed, and the block is projected with a velocity $v_ \mathrm { 1 } = 1.2 \mathrm {~m} / \mathrm { s }$ as it separates from the spring. The block descends a ramp and has a velocity $v_ 2 = 2.1 \mathrm {~m} / \mathrm { s }$ at the bottom. The track is frictionless between points A and B. The block enters a rough section at B, extending to E. The coefficient of kinetic friction between the block and the rough surface is 0.29. The velocity of the block is $v_ 3 = 1.4 \mathrm {~m} / \mathrm { s }$ at C. The block moves on to D, where it stops. How much work is done by friction between points B and C?

• A)-1.8 J
• B)-3.6 J
• C)-14 J
• D)-6.4 J
• E)-7.0 J

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