Trong mẫu chứa 1.49 μg khí 13 7N với chu kỳ bán rã t1/2 = 600 s. Hãy xác

định : số lượng hạt nhân 13

7N trong mẫu; hoạt độ phóng xạ của mẫu; hoạt độ

phóng xạ của mẫu sau 1 giờ.

Two identical 82 mg dust particles very far apart (pee 0) are moving directly toward each other at a speed of 3698 m/s. the charge on each is-719 ? c. determine how close they will get to each other. let k = 9x109 n-m2/c2 & ignore gravity.

Adding more pulleys to a system of pulleys needed to lift an object. a. increases the force b. decreases the force c. increases the amount of work d. decreases the amount of work

Lin yao looks at the back of a spoon. how should she describe her reflection? upside down and smaller upside down and larger right-side up and smaller right-side up and larger