What they look like

How the sensor works

The Photogate monitors the motion of objects passing through its gate, counting events as the object breaks the infrared beam. It measures the time it takes an object to pass through the beam. If the length(s) of the object is known, then its speed/velocity can be found using v=s/t. Some software programs allow the length of the object to be inputted and then the value of the velocity is given directly.

If two photogates are used in series, acceleration can be calculated. As the object passes through Gate1, initial velocity u can be calculated. The final velocity v can be calculated as it passes through the Gate 2.If the distance s between the gates is known, acceleration can be calculated using:

Where it can be used

The photogate can be used for a wide variety of experiments in physics and science classes.

• measuring velocity and acceleration
• measuring freefall acceleration.
• studying the swing of a pendulum.
• measuring the speed of a rolling object.
• timing the period of a rotating object.
• measuring the speed of objects undergoing collisions – momentum calculations