If `10^(20)` oxygen molecules per second strike `4cm^(2)` of wall at an angle of `30^(@)` with the normal when moving at a speed of `2xx10^(3)ms^(-1)`, find the pressure exerted on the wall. (mass of `1O_(2)` atom = `2.67xx10^(-26)kg`)

Explanation

Mass of `1O_(2)` atom `=2.67xx10^(-26)kg`
Mass of `10^(20)O_(2)` atom = `2.67xx10^(-26)kg`
`=26.72xx10^(-27)xx10^(20)`
Momentum P = mv
`=26.72xx10^(-7)xx8xx2xx10^(3)`
`=427.5xx10^(-4)kgms^(-1)`
Component of momentum normal to wall is `30^(@)`
`=427.5xx10^(-4)xxcos30^(@)`
`=427.5xx10^(-4)xx(sqrt(3))/(2)`
`=370.2xx10^(-4)kgms^(-1)`
Pressure = `(F)/(A) = ("Force (change in momentum)")/("area")`
`=(370.2xx10^(-4))/(4xx10^(-4))`
`P=92.55Nm^(-2)`