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Chrome File Edit View History Bookmarks people window Hep MasteringPhysics: PY21 1 Spr2016 mv #6 https:/l ID-608559798offset-next PY 211 General Physics Spring 2016 Problem 8.79 Problem 8.79 Part A A rifle bullet with mass 8.00 g strikes and embeds itself in a block with mass 0.992 kg that rests on a frictionless, horizontal surface and amached to a col spnrg. The impact compresses the spring 150 cm Calibration of the spring shows that a force of Q.750 N is required to compress the spring 0.250 cm Eun t) Find the magnitude of the blook's velocity just ather impact m/s My Answers Givee Part B What was the initial speed of the bullert? My Answers

Explanation / Answer

work done by a spring W= 0.5 k x^2

where k = spring constant .
all if the work done by the spring comes from the KE of the block
The bullet"s collision with the block is inelastic therefore only momentum is conserved.

spring constant = .750N/.250 = 3 N/m
assuming 0.250 is in meters.

KE of the block = work done by sping

0.5 (.992 +.008) V^2 = 0.5(0.375)(0.15^2)
v= SQRT((0.375)(0.15^2)/((.992 +.008))
V =0.2805 meters/sec is the speed of the block just after impact

speed of the bullet
momentum before collision = momentum after collision
.008 Vbullet = (.992 +.008) (.2805)

Vbullet = .2805/.008
=35.06 meters/sec

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