How do you calculate horse power in physical science?

That depends what data is provided.Horsepower is a unit of power (energy divided by time). Please note that the SI unit for power is the watt, not the horsepower. Of course, you can calculate watts, and then convert to horsepower.

Depending on the data provided, you can - for example - use the definition of power, as energy divided by time. In electricity, power is voltage x current (times a power factor, which is often close to one, and therefore not relevant).