What factor does the final velocity of the car change by if the height is doubled? STARTER #2

When this system is released from rest, it has potential energy. 1.How would you calculate the potential energy ? 2. What’s the KE when the mass hits the ground? When this system is released from rest, it has potential energy. 1.How would you calculate the potential energy ? 2. What’s the KE when the mass hits the ground? STARTER mgh ½(M+m)v 2

Conservation of Energy states: PE i + KE i = PE f + KE f Conservation of Energy states: PE i + KE i = PE f + KE f mgh = ½(M+m)v 2

Application - Energy Lab mgh = ½(M+m)v 2

Procedure 1.Adjust the string length so that the hanging weight hits the floor when the car is about 10cm from the pulley. 2.Release the car from rest and begin data collection for the motion detector. Take data until the weight hits the floor. 3.Catch the car before it hits the pulley! When not collecting data, set the car on its back so it does not roll off of the table. 4.Using the v vs. t graph, find and record the velocity where the weight hit the ground.

DATA Run # hanging mass (kg) Mass of car and contents (kg) V experimental (m/s) V theoretical (m/s)% Error

Questions 1.Usually, the actual velocity is smaller than the theoretical velocity. Why is this? 2.Why is the work done by gravity on the car zero? 3.Do your results support Conservation of Energy? Explain. 1.Usually, the actual velocity is smaller than the theoretical velocity. Why is this? 2.Why is the work done by gravity on the car zero? 3.Do your results support Conservation of Energy? Explain.

Lab Report Checklist  Coversheet  Data table  Calculations  Questions ( 3 )  Exit  Summary  Coversheet  Data table  Calculations  Questions ( 3 )  Exit  Summary

EXIT The acceleration of the car is given by: a = (mg)/(M+m) 1.For your first three runs, calculate the acceleration. 2. For your first three runs, use v f = at, and find the time it took in seconds for your car to reach its final velocity.