A rock once contained 1.0 mg of uranium-238, but now contains only 0.25 mg. Given that the half-life for uranium-238 is 4.5 x 109 (4.5 billion) years, how old is the rock?

Using a wheel and axle, a farmer is trying to lift a bucket of water from the bottom of a well. the larger wheel has a radius of 40 cm compared to the axle that has a radius of 10 cm. if a bucket of water is 50 n, then how much effort is required to raise it? 12.5 n 200 n 2 n 500 n

Could someone . i have tried to solve myself but my calculation is off

Which body part transports oxygen removes waste materials in carries nutrients to the body as part of the circulatory system