The decay rate of a radioactives ample is called its activity. What is the SI unit of activity?

The decay rate of a radioactive sample is called its activity. The half life of U_92^238 against alpha decay is 1.5x 10^17s . Calculate the activity of a sample of U_92^238 having 25 x 10^21 atoms.

What is the Si unit of pressure?

A large force acting for a short inerval of time is called impulsive force. What is the SI unit of impulse?

What is conductivity? Give its SI unit

What is the SI unit of mass? How is it defined?