Which of the following transforms an energy resource into electrical energy, and is a technology with no negative environmental impacts?

i. a coal-fired power plant
ii. a solar cell
iii. a wind turbine
iv. a hydroelectric dam

a.
i and ii only
b.
none of these
c.
iv only
d.
ii and iii only

An input force of 7 n is applied to a machine with a mechanical advantage of 1.75. what is the maximum the machine could lift? 12.25 n7n7.25 n26.2 n

A248-g piece of copper is dropped into 390 ml of water at 22.6 °c. the final temperature of the water was measured as 39.9 °c. calculate the initial temperature of the piece of copper. assume that all heat transfer occurs between the copper and the water. remember, the density of water is 1.0 g/m

You are given two vectors a⃗ =−3.00ι^ 5.00j^ and b⃗ =5.00ι^ 2.00j^. let the counterclockwise angles be positive.