Centripetal Force Lab CHALLENGE GET PUMPED

Objectives:

• to relate centripetal acceleration and Newton's second law: F = ma

Key Terms:

• velocity
• radius
• acceleration
• force
• mass
• average

Pre-Lab Discussion:

This lab connects Newton's second law, (F=ma), to centripetal acceleration, which is a relationship of the tangential velocity squared divided by the radius (a = V^2 / r ). In order to prove this relationship, we needed to measure force, velocity, mass, and radius. The rest of the this lab shows how we did this:

Our Setup and Materials:

• force probe
• Photogate
• ball
• string
• base and stand

Trial One Graph:

Radius: 0.495 meters

Trial Two Graph:

Radius: 0.35 meters


Analysis:

T R I A L  O N E 
Mass: 0.66  gram
Force: (see graphs - averaged force) 0.7463
a = Fm (F = ma)
 0.7463 = 0.66a
a = 11.30  m/s^2 (tangential)

or

Mass: 0.66 grams
Velocity: (see graphs - averaged velocity) 0.6387 m/s
Radius:  m
a = V^2/r
a = (0.6387^2)/(0.495)
a =  0.761 m/s^2 (centripetal)


T R I A L  T W O
Mass: 0.66 gram
Force: (see graphs - averaged force) 0.7488 N
a = Fm (F = ma)
0.7488 = 0.66a
a = 11.35 m/s^2 (tangential)

or

Mass: 0.66 grams
Velocity: (see graphs - averaged velocity) 0.5162 m/s
Radius: 0.35 m
a = V^2/r
a = (0.5162^2)/(0.35)
a = 0.824 m/s^2 (centripetal)

Overall Idea:

f=ma is used to find tangential velocity, whereas a = V^2/r is for finding the centripetal acceleration. In our lab, we expected to calculate the force, velocity, time, and acceleration of the system. We expected the acceleration of F = ma to equal the a of a = V^2/r, but, based on our results, that is not what was calculated.