A cyclist rides around a circular track at a uniform speed. Which of the following correctly gives the net horizontal force on the cyclist at any given instant of time?
Answer/Explanation
Markscheme
B
Cyclists moving in uniform speed
So its tangential acceleration will zero.
It means the net force in the direction of motion will be zero.
The only force act here is friction which will always be directed towards the centre of horizontal circle Friction \(= \frac{mv^2}{ r }\)
Which is non – zero
Nuclei of the isotope nitrogen-14 are bombarded with neutrons and as a result nuclei of an isotope of carbon are produced. The nuclear reaction equation for this process may be written as
\[_7^{14}{\rm{N}} + {\rm{neutron}} \to {}_6^A{\rm{C}} + {\rm{proton}}\]
What is the nucleon number A of the isotope of carbon?
A. 12
B. 13
C. 14
D. 15
Answer/Explanation
Markscheme
C
From the given statement ,what we know so far is that :
\(^{14}_{7}N+^{1}_{0}n\rightarrow ^{1}_{1}p\)
We can determine this mystery isotope by balancing the atomic and nucleon numbers.So,we balance basically all the top and bottom numbers..We let this mystery isotope be represented as :
\(^{14}_{7}N+^{1}_{0}n\rightarrow ^{1}_{1}p+^{m}_{z}X\)
So,our balancing goes as follows :
7+0=1+z
14+1=1+m
From here we get :
z=6
m=14
The element which has an atomic number of z=6 is carbon(C),therefore,X=C
\(^{14}_{7}N+^{1}_{0}n\rightarrow ^{1}_{1}p+^{14}_{6}C\)
The binding energy per nucleon of a \({}_1^3{\rm{H}}\) nucleus is 3 MeV. What is the minimum energy needed to
completely separate the nucleons of \({}_1^3{\rm{H}}\)?
A. 12 MeV
B. 9 MeV
C. 6 MeV
D. 3 MeV
Answer/Explanation
Markscheme
B
The Geiger–Marsden experiment provides evidence for
A. the existence of discrete atomic energy levels.
B. the existence of the neutron.
C. a dense positively charged nucleus.
D. the stability of some nuclei.
Answer/Explanation
Markscheme
C
The Geiger–Marsden experiments (also called the Rutherford gold foil experiment) were a landmark series of experiments by which scientists learned that every atom has a nucleus where all of its positive charge and most of its mass is concentrated.