Question

POD21-Prob#3) Energy A 4.5 kg block is thrust upward along a 30° incline plane with an initial speed of Vo=5.0m/s. It travels a distance of 1.5m up the plane before coming to rest. a. How much internal energy does the system of block + plane+Earth gain in the process due to friction? Hint: ...beware the sign b. The block then slides from rest back down the plane. Assuming friction to produce the same "gain" in internal energy during the downward journey, what is the speed of the block at the instant it passes through its original location?

Answer 1

mass of the block m 4.5kg velocity v-5.0m/s mv2 initial kinetic energy K maximum potential energy of the mass when it climb height h- U- mgh mgh -4.5kgx9.8x 1.5sin(30)- 33.075J energy lost due to friction- Ef K-U 23.175J 56.250J a)internal energy of the sytem gained in this process-energy lost due to friction in the form of heat 23.175J b) height reached by block h 1.5sin(30)-0.75m potential c ncrgy of the block-U-mgh 33.075J if the enrgy lost due to frictionis Ef-23.175J kinetic energy left by the time the block pass original location -K'-U- Ef-9.90J speedof the blockeysV2K' =2.0976m/