AP Physics Variables to Measure and their Units Variable Symbol Units Measuring Device acceleration m/s2 mᐧs-2 accelerometer meterstick + stopwatch meterstick + photogates Lab carts with motion sensors embedded motion detectors Smart Pulley (needs constant net Force) video analysis Amplitude (of a wave or oscillation) m meterstick Protractor distance m meterstick calipers (small) laser guide (big) energy J kgᐧm2/s2 kgᐧm2ᐧs-2 (calculated not directly measured) frequency Hz 1/s s-1 stopwatch photogates force N kgᐧm/s2 kgᐧmᐧs-2 spring scale force probe Cart with force probe Bathroom scale rotational inertia kgᐧm2 (calculated not directly measured) based on the shape of the object if shape is known: scale and meter stick kinetic energy J kgᐧm2/s2 kgᐧm2ᐧs-2 (calculated not directly measured) way to determine mass and velocity (balance, photogates, meterstick) spring constant N/m Nᐧm-1 kg/s2 kgᐧs-2 (calculated not directly measured) spring scale/force probe and calipers/meterstick angular momentum kgᐧm/s kgᐧmᐧs-1 (calculated not directly measured) If L is known, then measure radius (meterstick) and period (stopwatch) length m meterstick calipers (small) laser guide (big) a A d E ƒ F I K k L ℓ m mass kg balance (not a scale! scales measure the normal force not weight) power W J/s Js-1 wattmeter momentum kgᐧm/s kgᐧmᐧs-1 (calculated not directly measured) Balance for mass and photographs/meterstick for velocity radius or separation m meterstick calipers (small) laser guide (big) period s stopwatch photogate video analysis time s stopwatch photogate video analysis potential energy J kgᐧm2/s2 kgᐧm2ᐧs-2 (calculated not directly measured) meterstick for height and balance for mass volume m3 (calculated not directly measured) based on the shape of the object graduated cylinder speed or velocity m/s mᐧs-1 (calculated not directly measured) photogates and meterstick motion sensor video analysis work done on a system J Nm kgᐧm2/s2 kgᐧm2ᐧs-2 (calculated not directly measured) meterstick for distance and force probe for force position m meterstick calipers (small) laser guide (big) video analysis height m meterstick calipers (small) laser guide (big) video analysis angular acceleration rad/s2 radᐧs-2 (calculated not directly measured) revolutions per time unit (stopwatch) rotary motion sensor P p r T t U V v W x y α coefficient of friction (none) (calculated not directly measured) Dependent on the surface. If frictionless, it’s zero. angle rad protractor A circle is 2𝝅 radians density kg/m3 (calculated not directly measured) mass (balance) divided by volume (graduated cylinder) resistivity Ωᐧm (calculated not directly measured) torque J Nm kgᐧm2/s2 kgᐧm2ᐧs-2 (calculated not directly measured) force probe and meterstick and protractor angular speed rad/s radᐧs-1 (calculated not directly measured) revolutions (counted) per time (stopwatch/photogate) rotary motion sensor area m2 meterstick current A C/s multimeter q charge C (calculated not directly measured) R resistance Ω kgm2s-3A-2 multimeter electrical potential V J/C multimeter μ θ ⍴ ⍴ 𝜏 ⍵ A I V
