00:01
In this problem, a motor drives a pump which raises 10 ,800 kg per hour, right? and the water of you can say 5 meter, right? so it is asked that what is the power rating of the motor if the power efficiency is 100%, 70 % and 40%.
00:40
So this is basically it has asked the power rating.
00:48
So here what will be the output bar, right? to calculate the input power.
01:06
Is it that same thing? because input will be something which has rated back.
01:13
Okay.
01:14
So can you write it as let us say this, let us delete this per hour is written this so can we write in 1 r means 1 r in t equals to 1 r you can say that mass m 10 ,800 kg in t that means 1 r which is nothing but which is in seconds will be 60 into 60 right which will be 3 600 seconds right now what is height here height is represented as h here equals to five meters right so now um you can see here that you can also understand that power is given by power is given by work upon time right let us say this is work and this is time t right so let us say uh output work i'm writing because you may not get not output it should be output power.
02:42
So this should be equals to mgh upon t here, right? mgh is the for edge height, you can say the work done, right? so this is equal to what? they should be equals to 10 ,800 kg into g is, gravitational acceleration that is that value is 9 .8 meter per second please if you are confused with the units you must write it so that you may know that where it is getting cancelled right so this is multiplied with 5 meter and this is divided by in how many seconds right here because unit you can see here that 9 .8 that is taken in meter per second.
03:50
So we must take time in the same units that is 3 ,600 seconds here.
03:57
Right.
03:58
So now we will be getting output power...