The net weight of the balloon must be zero.
The forces acting on the hot-air balloon when it hovers at a fixed altitude are gravitational force and the upthrust of the hot air. As the balloon is at a fixed altitude, the two forces balance each other resulting in zero net force. Thus, the weight of the balloon is balanced by the upthrust, so the balloon is weightless at this time of the flight.
Proton: symbol P, + 1
neutron: symbol n, 0
Electron: symbol e, -1
That thing is used as a lever.
Physical changes do not change the identity of the substance. Heat causes chemical reactions. You cannot see chemical changes with the naked eye. The identity of a substance changes like when you burn paper, from paper it turns into ash and produces smoke, which are products from the chemical reactions.
<u>Answer:</u> The remaining sample of X is 6.9 grams.
<u>Explanation:</u>
All the radioactive reactions follow first order kinetics.
The equation used to calculate rate constant from given half life for first order kinetics:
We are given:
Putting values in above equation, we get:
The equation used to calculate time period follows:
where,
= initial mass of sample X = 78 g
N = remaining mass of sample X = ? g
t = time = 16.5 min
k = rate constant =
Putting values in above equation, we get:
Hence, the remaining amount of sample X is 6.9 g