What is the cause of friction?

What is the cause of refraction?

Explain why friction is necessary to make the disc in Fig. 7.41 roll in the direction indicated. (a) Give the direction of frictional force at B, and the sense of frictional torque, before perfect rolling begins. (b) What is the force of friction after perfect rolling begins?

What is the cause of Adsorption?

To maintain a rotor at a uniform angular speed of 200 rad s~ 1, an engine needs to transmit a torque of 180 Nm. What is the power required by the engine? (Note: uniform angular velocity in the absence of friction implies zero torque. in practice, applied torque is needed to counter frictional torque). Assume that the engine is 100 % efficient.

What is the cause of excess pressure inside a soap bubble?

What is the main cause of charge on a colloidal solution?