Physics 211 Momentum Review Problems To determine the speed of a bullet, it is f

Question

Physics 211 Momentum Review Problems To determine the speed of a bullet, it is fired into a block of wood. The wooden block is attached by a rod to a low 3. friction axde. The bullet becomes embedded in the wood and the maximum angle the rod rotates is measured a. Use the numbers in the diagram to determine the speed 300 % of the bullet. Hint: start by using the angle to determine the speed of the block and bullet just after the bullet 0.8 m becomes embedded in the wood. b. How much mechanical energy was lost during the collision? Camment: You should find that most of the mechanical energy was lost c. Where did this mechanical energY go? 0.8 kg 4 grams

Explanation / Answer

Applying energy conservation after the collision,

PEi + KEi = PEf + KEf

0 + m v^2 /2 = m g L (1 - cos30) + 0

v = sqrt(2x 9.8 x 0.8 x (1 - cos30))

v = 1.45 m/s

Now applying momentum conservation for the collision,

(0.004)(v0) + (0.8 x 0) = (0.8 + 0.004)(1.45)

v0 = 291 m/s ......Ans

(B) Ki = (0.004)(291^2)/2 = 169.7 J

Kf = (0.8 + 0.004)(1.45^2)/2 = 0.85 J  

energy lost = Ki- Kf = 169 J ....Ans

(C) This energy converted in other form.

as sound, heat energy

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