Which of the following statements about a moving object is correct?
When accelerating, the resultant force acting on it must be equal to zero.
There must always be a non-zero resultant force acting on it.
At a steady velocity, the resultant force acting on it must be equal to zero
At a steady velocity, the air resistance must be equal to zero.
Correct answer is C
No explanation has been provided for this answer.
| Radio wave | Micro wave | Infrared wave | P | Q | R | Gamma Ray |
The table above shows the components of electromagnetic spectrum in order of increaasing frequency.Which of the following sets correctly identifies P, Q, R respectively?
Visible, ultraviolet, X-ray
X-ray, visible, ultraviolet
Ultraviolet, visible, X-ray
X-ray, ultraviolet, visible
Correct answer is A
No explanation has been provided for this answer.
Which of the following statements about Gamma radiation is correct? Gamma radiation can
be seen by the naked eye
not pass through an aluminium foil
be present naturally in our surroundings
be used as a tracer
Correct answer is D
No explanation has been provided for this answer.
| n = α | 0.06eV |
| E=3 | -1.6eV |
| E=2 | -3.7eV |
| E=1 | -5.5eV |
| E=0 | -10.4eV |
The energy levels in the mercury atom is illustrated in the table above. Calculate the ionisation energy of the atom.
+21.2eV
+10.4eV
-10.4eV
-21.2eV
Correct answer is B
No explanation has been provided for this answer.
The nucleon number of an atom is the total number of
electrons and protons
electrons and neutrons
neutrons minus electrons
protons and neutrons
Correct answer is D
No explanation has been provided for this answer.