Answer:
(a) 
(b) 15 hours
Explanation:
half life, T = 12 hours
No = 19 g
(a) Let N be the amount remaining after time t.
Let λ be the decay constant.

The equation of radioactivity used here is given by


(b) N = 8 gram
Substitute the values in above equation

λ = 0.0577 per hour
So, 

Take natural log on both the sides
- 0.0577 t = - 0.865
t = 15 hours
Question: If a car is moving on a road at 70 km/hr going due north, and then changes direction and starts traveling north-east staying at 70 km/hr, what happens to its speed and velocity?
Answer: the velocity of the car changes, but the speed stays the same.
Explanation: basically velocity is speed with a direction and speed is the absolute value or magnitude of velocity.
question answered by
(jacemorris04)
<u>Answer:</u>
Specific Heat
<u>Explanation:</u>
Specific heat is the measurement which describes the amount of heat needed to raise the temperature of one gram of a material by one degree Celsius.
It is the amount of heat required per unit mass to raise the temperature by one degree Celsius. The relationship between heat and the temperature change is usually expressed as shown below:
Δ
where
= heat added,
= specific heat,
=mass; and
Δ
= change in temperature