If the lightbulb A in the circuit shown in the image burned out, the path for the current to flow is disrupted because one of its terminals is connected direct to the source. So, there will be no current through the lightbulbs B, C, and D, and they will turn off. Similarly it will happen, if the lightbulb D burned out.
If the lightbulb B burned out the current will continue circulating through the lightbulbs A, C, and D, because lightbulb B is connected in parallel. Similarly it will happen, if the lightbulb C burned out.
If you mean climate change. Then scientists can study it by seeing where places and things are eroded.
The ration of output work to input work expressed as a percentage is called <u>Efficiency</u>.
Here we apply conservation of linear momentum. The momentum of the truck with cargo and without cargo remains constant. That is,
.
Here 
are initial mass and velocity. 
are final mass and velocity. Here 
and 
.
The velocity of the truck be after its cargo is taken off is
