When a machine is used to do work, the force applied by the machine is called the effort force?

An object weigh 40n in air ,weigh 20n when submerged in water,and 30n when submerged in a liquid of unknown liquid density.what is the density of unknown of liquid?

A1000-kg car is moving at 30 m/s around a horizontal unbanked curve whose diameter is 0.20 km. what is the magnitude of the friction force required to keep the car from sliding?

The crank oa rotates in the vertical plane with a constant clockwise angular velocity ω0 of 3.2 rad/s. for the position where oa is horizontal, calculate the force under the light roller b of the 12.9-kg slen