Paper 1 Gravitational Fields Drills

Q1

Newton’s law of gravitation gives the magnitude of the force between point masses as

A. $G{m}_1{m}_2{r}^2$
B. $G{m}_1{m}_2/r^2$
C. $G(m_1+m_2)/r$
D. $Gm/r$

Q2

If the separation between two point masses is doubled, the gravitational force becomes

A. twice as large.
B. half as large.
C. one quarter as large.
D. four times as large.

Q3

Gravitational field strength is defined as

A. force per unit mass.
B. force per unit charge.
C. energy per unit mass.
D. work done per unit time.

Q4

The SI unit of gravitational field strength is

A. $\mathrm{N}\mathrm{k}{\mathrm{g}}^{-1}$
B. $\mathrm{N}{\mathrm{m}}^{-1}$
C. $\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}$
D. $\mathrm{kg}{\mathrm{N}}^{-1}$

Q5

The gravitational field due to a single isolated mass points

A. away from the mass.
B. towards the mass.
C. tangent to a circle around the mass.
D. in the direction of motion of a test mass.

Q6

Gravitational potential at a point is

A. force per unit mass.
B. work done per unit mass in bringing a small mass from infinity to the point.
C. work done per unit mass in moving around any closed path.
D. acceleration per unit mass.

Q7

With zero potential at infinity, the gravitational potential near an isolated mass is

A. positive.
B. negative.
C. always zero.
D. independent of distance.

Q8

For a point mass $M$, gravitational potential is

A. $GM/r$
B. $-GM/r$
C. $GM/r^2$
D. $-GM/r^2$

Q9

Gravitational potential is a

A. vector.
B. scalar.
C. force.
D. displacement.

Q10

At a point between two equal masses, the gravitational field strength at the midpoint is

A. zero.
B. maximum.
C. directed towards both masses at once with double magnitude.
D. equal to the potential.

Q11

At the same midpoint between two equal masses, the gravitational potential is

A. zero because the fields cancel.
B. the algebraic sum of the two negative potentials.
C. a vector pointing left.
D. a vector pointing right.

Q12

A satellite in a circular orbit is kept in orbit because gravity provides

A. tangential force.
B. outward force.
C. centripetal resultant force.
D. zero force.

Q13

For a circular orbit around mass $M$, orbital speed satisfies

A. $v=\sqrt{GM/r}$
B. $v=GMr$
C. $v=\sqrt{g{r}^2}$
D. $v=GM/r^2$

Q14

In a higher circular orbit around Earth, orbital speed is

A. larger.
B. smaller.
C. unchanged.
D. zero.

Q15

A geostationary satellite must have an orbital period of approximately

A. $1$ hour.
B. $12$ hours.
C. $24$ hours.
D. $1$ month.

Q16

A geostationary orbit must be

A. above the equator and in the direction of Earth’s rotation.
B. above the poles.
C. any circular orbit with radius equal to Earth’s radius.
D. elliptical and inclined.

Q17

The magnitude of gravitational field strength outside a spherical planet is

A. proportional to $r^2$.
B. proportional to $1/r^2$.
C. proportional to $r$.
D. independent of $r$ at all distances.

Q18

The relationship between radial gravitational field strength and potential is that field strength is linked to

A. the potential gradient.
B. the potential itself only.
C. the square of potential.
D. the orbital period only.

Q19

The gravitational force between two masses is always

A. repulsive.
B. attractive.
C. zero in space.
D. perpendicular to the line joining centres.

Q20

For a test mass $m$ in potential $\varphi$, gravitational potential energy is

A. $m\varphi$
B. $\varphi /m$
C. $mg/r$
D. $Gm/r^2$