Yang Gao
Chen peng Tong
Dynamic

Introduction:
The purpose of this experiment is to explore kinetic and potential energy are transformed into each other and the amount of mechanical energy is unchanged, it’s only occur in the case without taking into account the friction and dielectric resistance,. (The potential energy is divided into gravitational potential energy and elastic potential energy)

Theory:
We define work as force acting over a specified displacement. When we look at a system, we must look at the total energy allowed in the system. Therefore, we have
W = F d⃗
Potential is the ability to have to do something, and energy is the force applied over a displacement. Thus, potential energy is the ability to apply a force over a displacement. The most common and easiest to understand of the potential energy is Gravitational Potential Energy, or for short, GPE. Mathematically, it is defined as:
GPE = mgh
We now introduce Kinetic Energy, denoted as KE. This is a measure of the energy possessed by the movement of an object with mass. We mathematically define it as:
KE =1/2mv2
Next we have the potential energy stored by a spring. When we compress or stretch a string with a force, whatever work we are applying to the spring is being stored within in. We have the following formula for the energy stored within a spring:
EPE =1/2kx2
Material:
Springs photo gate
Car Air cushion track
Procedure:
Experiment1: 1. Measure the K and distance of the spring . 2. Connect the car and the spring, then put them and photo gate on the air cushion track. 3. Stretch the spring, and measure the length. Then, release the car through the photo gate, and record the time. 4. Change the spring length, and do 3 trials.
Experiment2:
1. change the height of the car, measure the height between car and photo gate, and record the time of the car go through photo gate, and do 3 trials.

DATA:
Experiment1
| Distance Stretched (m) | Time(s) | Velocity (m/s) | EPE (J) | KE (J) | Percent Error (%) | Trial 1 | 0.175 | 0.104 | 0.959 | 0.100 | 0.092 | -8.083 | Trial 2 | 0.135 | 0.135 | 0.743 | 0.060 | 0.055 | -7.382 | Trial 3 | 0.115 | 0.154 | 0.649 | 0.043 | 0.042 | -2.881 |
Experiment2
| Height (m) | Height Photogate(m) | Time (s) | Velocity (m/s) | KE (J) | GPE (J) | Percent Error (%) | Trial 1 | 0.255 | 0.190 | 0.009 | 1.106 | 0.12 | 0.13 | -4.12 | Trial 2 | 0.255 | 0.210 | 0.110 | 0.091 | 0.08 | 0.09 | -9.39 | Trial 3 | 0.255 | 0.170 | 0.008 | 1.234 | 0.15 | 0.17 | -8.74 |

Calculation: