4. A 100 kg crate sits on the concrete floor of a warehouse. The static coefficient of friction of wood on concrete is .62. Kinetic is 55.

a Calculate the force needed to get the crate moving from rest.

b. Calculate the force needed to keep the crate sliding at a constant velocity

Calculate the force needed to accelerate at 3.2 m/s.

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?

Inside of a windmill or a dam is a that is used to transform one type of energy into electrical energy. a. motor b. generator c. transformer d. power pack

Currents in dc transmission lines can be 100 a or higher. some people are concerned that the electromagnetic fields from such lines near their homes could pose health dangers. for a line that has current 150 a and a height of 8.0 m above the ground, what magnetic field does the line produce at ground level? express your answer in teslas and as a percentage of the earth’s magnetic field, which is 0.50 g. is this value cause for worry?