Answer:
3.87 or 3.9 mg
Explanation:
2.7h * 60mins = 162mins
number of 1/2 lives = 162/22= 7.364
amount remaining = 639(1/2)^7.364 = 3.8796
answer = 3.87 or 3.9
Explanation:
Weight (N) = Mass * Acceleration
75.74 kg = Mass * 9.8 m/sec^2
Mass = 7.72 kg
Weight = 75.74 N
If an object is moving with a constant velocity, then by definition it has zero acceleration. So there is no net force acting on the object. The total work done on the object is thus 0 (that's not to say that there isn't work done by individual forces on the object, but the sum is 0 ).