1. Have scientists been able to invent a perpetual motion machine?
O Yes
O No

Which is the layer underground where all empty spaces are filled with a combination of air and water ?

To find the enthalpy of a reaction in the lab, you measured the of the reactants and the change during the reaction.

Ariver current has a velocity of 5km/h relative to the shore, and a boat moves in the same direction as the current at 5 km/h relative to the river. how can the velocity of the boat relative to the shore be calculated?