A bullet is fired horizontally at into the center of a wooden block that can slide…
PHYSICS · Multi-part · CBSE · Physics · Work, Energy and Power · Work, Energy and Power
Problem
A 10g bullet is fired horizontally at 450ms−1 into the center of a 1.2kg wooden block that can slide without friction on a horizontal table. The block is attached by a light, inextensible string over a frictionless pulley to a 0.80kg hanging mass that is initially at rest 0.50m above the floor, as shown in the side view below (no diagram is provided).
The bullet embeds in the block and remains inside. The collision time is 2.0ms. Neglect air resistance.
(a) Immediately before and after the collision, identify a choice of system for which linear momentum in the horizontal direction is conserved. Justify your choice by discussing external forces on that system during the 2.0ms interval.
(b) Using the system chosen in part (a), calculate the speed of the block–bullet combination immediately after the collision.
(c) After the collision, the block begins to move, causing the hanging mass to rise. Determine the maximum height the hanging mass reaches before momentarily coming to rest. Clearly indicate any additional principles you use beyond momentum conservation.
(d) Suppose a student had treated only the bullet as the system in part (b). Explain qualitatively how this incorrect system choice would affect the calculated speed of the block–bullet combination, and why.