Physics 9702 · AS & A Level · Gravitational force between point masses
Gravitational force between point masses — practice question
A binary star is made up of two stars A and B that move round each other, as shown in Fig. 1.1. The stars follow circular orbits whose centres are at point P, which is a distance $d$ from the centre of star A.
(a(i))[2]
Explain why the centripetal force on both stars has equal magnitude.
(a(ii))[2]
The stars take 4.0 years to complete an orbit about point P. Calculate the angular speed $\omega$ of the stars.
(b(i))[3]
The centres of the stars are $2.8 \times 10^8\ \text{km}$ apart. The mass of star A is $M_A$. The mass of star B is $M_B$. The ratio $\frac{M_A}{M_B}$ is $3.0$. Determine the distance $d$.
(b(ii))[3]
Use your answers in (a)(ii) and (b)(i) to find the mass $M_B$ of star B. Explain your working.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Gravitational force acts as/is the centripetal force” …