1. A satellite is in a circular orbit of radius $R$ around a planet of mass $M$. Which of the following graphs represents the relationship between the centripetal acceleration of the satellite and its orbital radius?

A.				B.
C.				D.

2. Two positive charges of magnitude $2C$ and $8C$ respectively are placed 9cm apart. A third charge is introduced between the two charges as shown below;

At what separation, X, from the 2C charge is the electric field strength equal to zero?

3. Satellites $A$ and $B$ orbit the same planet of mass $M$. Satellite $A$ has a mass of $3m$ and it is located at a height of $R$ from the surface of the planet. Satellite $B$ has a mass of $m$ and it is located at a height of 2$R$ from the surface of the planet.

What is the ratio of the centripetal force acting on $A$ to the centripetal force acting on $B$?

4. Two stars of equal mass $M$ are shown in the diagram, distance $d$ apart. A planet is equidistant from the two stars, with distance d/2 across the midpoint of the line joining the stars as shown.

What is the resultant gravitational field strength at the position of the planet due to the two stars?

5. Planet $A$ has a gravitational field strength $g$ at its surface. Planet $B$ has twice the density and twice the radius of planet $A$.

What is the gravitational field strength at the surface of $B$?

6. Two positive charges q1 and q2 are separated by a distance $d$. A third positive charge $q$ is placed at a distance d/4 from q1 so that the charge $q$ is in equilibrium.

What is the ratio q1/q2?

7. Which of the following graphs shows the variation of the gravitational field strength of a planet with distance $r$ from the surface of a planet?

A.			B.
C.			D.

8. Planet $X$ has radius $R$ and density $\rho$. The gravitational field strength at the surface of Planet $X$ is $g$.

What is the ratio of the gravitational field strength at the surface of planet Y, which has radius 0.25$R$ and density 3$\rho$, to that at the surface of Planet X?

9. A conductor carrying electric current out of the plane of the paper is placed between two magnets as shown in the diagram.

At which location is the magnitude of the resultant magnetic field strength largest due to the conductor and the magnets?

10. A charge of $X$ and a charge of $20nC$ are held at a fixed distance.

A point where the electric field is zero can only be found in region 1. Which of the following statements is true about the charge on $X$?

11. An object of mass $m$ and charge $q$ is dropped vertically between two parallel plates, $K$ and $L$. A magnetic field $B$ can be created perpendicular to the plane of the paper. The electric field between plates is $E$.

Which of the following is correct about the magnitude of magnetic and electric fields when the object falls vertically at a constant velocity v?

12. Which of the following is correct about the gravitational field strength at a point near a planet?

13. A beam of electrons enters a uniform electric field, as shown.

What effect does this field have on the horizontal and vertical components of the electrons' velocity?

14. The centers of three masses lie on the same line. The centers of the masses are separated as shown.

The net gravitational force on m2 is zero when the value of $d$ is one third of $x$. What is the ratio m1/m3?

15. A positive and a negative charge of equal magnitude are located on the same horizontal line.

What is the direction of the net electric field at the point marked X, equidistant from the two charges?

16. The diagram shows the gravitational field between two masses m1 and m2.

Which of the following is correct?

17. Two sections of current-carrying wires, $X$ and $Y$, that lie in the plane of the paper, are shown below. The arrow in wire $X$ shows the direction of conventional current. Which response gives possible directions of current in wire $Y$ and electromagnetic force acting on $Y$?

18. A wire is carrying a current $I$ is placed in a region of uniform magnetic field B1. The magnitude of the magnetic field is $B$, and its direction is into the page. The force acting on the wire is $F$, as shown in the diagram.

The wire, carrying the same current $I$, is now placed with the orientation shown into another region of uniform magnetic field B2. The magnitude of the magnetic field is $B$, and its direction is out of the page.

What is the correct direction and magnitude of the force acting on the wire in field B2?

	Direction	Magnitude
A.		$F$
B.		$F$
C.		$F\sin \theta$
D.		$F\sin \theta$

19. Two point charges are separated by a distance $r$ as shown.

20. Estimate the speed of an alpha particle that has accelerated from rest in a uniform electric field E=50NC^−1 over a distance of 2.0m.

21. A satellite $X$ is in a circular orbit of radius $R$ with a period $T$ around Earth.

What will be the orbital radius of satellite Y, travelling in a circular orbit with a period of 8$T$ around Earth?

22. Two charges separated by a distance $r$ are placed in a medium with permittivity $ϵ$. The charges are then moved to air so that they have the same force between them as that in the medium.

23. A current-carrying wire is at right angles to a uniform magnetic field. The magnetic force per unit length on the wire is F/L. The length of the wire, the magnitude of the magnetic field strength, and the current of the wire are all doubled. Which of the following is the magnetic force per unit length on the wire after these changes?

An alpha particle of mass m and charge $q$, is accelerated through a potential difference $V$ into a magnetic field of flux density $B$ that is at right angles to the direction of motion. Which of the sketches below best describes the relationship between the radius of path $r$ and the potential difference of the accelerating field?

24.

A.			B.
C.			D.

25. A proton and another object with charge +e exert electrical and gravitational forces on one another. To the nearest order of magnitude, what mass must the object have to be so that the net force acting on it is zero?