Sand from a stationary hopper falls onto a moving conveyor belt at the rate of 5.00 kg/s as shown in Figure P9.94. The conveyor belt is supported by frictionless rollers and moves at a constant speed of v 5 0.750 m/s under the action of a constant horizontal external force F S ext supplied by the motor that drives the belt. Find (a) the sands rate of change of momentum in the horizontal direction, (b) the force of friction exerted by the belt on the sand, (c) the external force F S ext , (d) the work done by F S ext in 1 s, and (e) the kinetic energy acquired by the falling sand each second due to the change in its horizontal motion. (f) Why are the answers to parts (d) and (e) different?

PHY 184 Week 9 Notes-Magnetic Fields & Electromagnetic Induction 10/24-10/27 Moving charges produce a magnetic field o The Biot-Savart Law establishes this relation Wires produce a magnetic field o Can be seen by a compass near the wires μ d B= 0 ids×^ ⏞= ⃗ o 4π r2 ; r μ0 is the magnetic permeability of free space 4π 10 -7 To calculate B at P just integrate along the path Solving for B using symmetry gives B= μ0i o 2πd 2 Parallel Wires Consider a wire with current i a d1stance d away, with another wire nearby with current i .2 o They will attract Magnetic Force is given by F=i2L B1si