AP Physics   Chapter 13  Review Sheet

1.	In the formula F = Gm1m2/r2, the quantity G: 	
A)	depends on the local value of g 	
B)	is used only when the Earth is one of the two masses 	
C)	is greatest at the surface of the Earth 	
D)	is a universal constant of nature 	
E)	is related to the Sun in the same way that g is related to the Earth 	

2.	Suitable units for the gravitational constant G are: 	
A)	kg×m/s2	
B)	m/s2	
C)	N×s/m 	
D)	kg×m/s 	
E)	m3/(kg×s2) 	

3.	Earth exerts a gravitational force on the Moon, keeping it in its orbit. The reaction to this force, in the sense of Newton's third law, is: 	
A)	the centripetal force on the Moon 	
B)	the nearly circular orbit of the Moon 	
C)	the gravitational force exerted on Earth by the Moon 	
D)	the tides due to the Moon 	
E)	the apple hitting Newton on the head	

4.	Three particles, two with mass m and one mass M, might be arranged in any of the four configurations known below. Rank the configurations according to the magnitude of the gravitational force on M, least to greatest.

A)	1, 2, 3, 4	
B)	2, 1, 3, 4	
C)	2, 1, 4, 3	
D)	2, 3, 4, 2	
E)	2, 3, 2, 4	

5.	Let F1 be the magnitude of the gravitational force exerted on the Sun by Earth and F2 be the magnitude of the force exerted on Earth by the Sun. Then: 	
A)	F1 is much greater than F2	
B)	F1 is slightly greater than F2	
C)	F1 is equal to F2	
D)	F1 is slightly less than F2	
E)	F1 is much less than F2	

6.	Venus has a mass of about 0.0558 times the mass of Earth and a diameter of about 0.381 times the diameter of Earth.  The acceleration of a body falling near the surface of Venus is about:	
A)	0.21 m/s2	
B)	1.4 m/s2	
C)	2.8 m/s2	
D)	3.8 m/s2	
E)	25 m/s2	

7.	A rocket ship is coasting toward a planet. Its captain wishes to know the value of g at the surface of the planet. This may be inferred by: 	
A)	measuring the apparent weight of one of the crew 	
B)	measuring the apparent weight of an object of known mass in the ship 	
C)	measuring the diameter of the planet 	
D)	measuring the density of the planet 	
E)	observing the ship's acceleration and correcting for the distance from the center of the planet	

8.	Suppose you have a pendulum clock which keeps correct time on Earth (acceleration due to gravity = 9.8 m/s2). Without changing the clock, you take it to the Moon (acceleration due to gravity = 1.6 m/s2). For every hour interval (on Earth) the Moon clock will record:	
A)	(9.8/1.6) h 	
B)	1 h	
C)		
D)	(1.6/9.8) h	
E)		

9.	An astronaut on the Moon simultaneously drops a feather and a hammer. The fact that they land together shows that: 	
A)	no gravity forces act on a body in a vacuum 	
B)	the acceleration due to gravity on the Moon is less than g on the Earth 	
C)	in the absence of air resistance all bodies at a given location fall with the same acceleration 	
D)	the feather has a greater weight on the Moon than on Earth 	
E)	G = 0 on the Moon 	

10.	An object at the surface of Earth (at a distance R from the center of Earth) weighs 90 N. Its weight at a distance 3R from the center of Earth is: 	
A)	10 N 	
B)	30 N 	
C)	90 N 	
D)	270 N 	
E)	810 N 	

11.	A spring scale, calibrated in newtons, is used to weigh sugar. If it were possible to weigh sugar at the following locations, where will the buyer get the most sugar to a newton? 	
A)	At the north pole 	
B)	At the equator 	
C)	At the center of Earth 	
D)	On the Moon 	
E)	On Jupiter 	

12.	If Earth were to rotate only 100 times per year about its axis: 	
A)	airplanes flying west to east would make better time 	
B)	we would fly off Earth's surface 	
C)	our apparent weight would slightly increase 	
D)	Earth's atmosphere would float into outer space 	
E)	our apparent weight would slightly decrease 	

13.	Each of the four corners of a square with edge a is occupied by a point mass m.  There is a fifth mass, also m, at the center of the square.  To remove the mass from the center to a point far away the work that must be done be an external agent is given by:	
A)	4Gm2/a 	
B)	–4Gm2/a 	
C)	 	
D)	 	
E)	4Gm2/a2	

14.	The escape velocity at the surface of Earth is approximately 8 km/s. What is the mass, in units of Earth's mass, of a planet with twice the radius of Earth for which the escape speed is twice that for Earth?	
A)	2	
B)	4	
C)	8	
D)	1/2	
E)	1/4	

15.	Neglecting air resistance, the escape speed from a certain planet for an empty space vehicle is 1.12 ´ 104 m/s. What is the corresponding escape speed for the fully loaded vehicle which has triple the mass of the empty one? 	
A)	3.73 ´ 103 m/s 	
B)	1.12 ´ 104 m/s 	
C)	3.36 ´ 104 m/s 	
D)	9.98 ´ 104 m/s 	
E)	1.40 ´ 1012 m/s 	

16.	A projectile is fired straight upward from Earth's surface with a speed that is half the escape speed. If R is the radius of Earth, the highest altitude reached, measured from the surface, is: 	
A)	R/4 	
B)	R/3 	
C)	R/2 	
D)	R 	
E)	2R 	

17.	A spherical shell has inner radius R1, outer radius R2, and mass M, distributed uniformly throughout the shell. The magnitude of the gravitational force exerted on the shell by a point mass m a distance d from the center, inside the inner radius, is: 	
A)	0 	
B)	 	
C)	GMm/d2	
D)	 	
E)	GMm/(R1 – d)2	

18.	A spherical shell has inner radius R1, outer radius R2, and mass M, distributed uniformly throughout the shell.  The magnitude of the gravitational force exerted on the shell by a point particle of mass m, located a distance d from the center, outside the inner radius and inside the outer radius, is:	
A)	0 	
B)	GMm/d2 	
C)	 	
D)	 	
E)	 	

19.	An astronaut finishes some work on the outside of his satellite, which is in circular orbit around the Earth. He leaves his wrench outside the satellite. The wrench will: 	
A)	fall directly down to the Earth 	
B)	continue in orbit at reduced speed 	
C)	continue in orbit with the satellite 	
D)	fly off tangentially into space 	
E)	spiral down to the Earth 	

20.	Consider the statement: "Earth moves in a stable orbit around the Sun and is therefore in equilibrium". The statement is: 	
A)	false, because no moving body can be in equilibrium 	
B)	true, because the Earth does not fall into or fly away from the sun 	
C)	false, because the Earth is rotating on its axis and no rotating body can be in equilibrium 	
D)	false, because the Earth has a considerable acceleration 	
E)	true, because if it were not in equilibrium then buildings and structures would not be stable 	

21.	In planetary motion the line from the star to the planet sweeps out equal areas in equal times. This is a direct consequence of: 	
A)	the conservation of energy 	
B)	the conservation of momentum 	
C)	the conservation of angular momentum 	
D)	the conservation of mass 	
E)	none of the above 	

22.	A planet travels in an elliptical orbit about a star as shown. At what pair of points is the speed of the planet the same?

A)	W and S 	
B)	P and T 	
C)	P and R 	
D)	Q and U 	
E)	Vand R	

23.	For a planet in orbit around a star the perihelion distance is rp and its speed at perihelion is vp.  The aphelion distance is ra and its speed at aphelion is va.  Which of following is true?	
A)	va = vp	
B)	va/ ra = vp/rp	
C)	va ra = vp rp	
D)	va/ r2a = vp/r2p	
E)	va r2a = vp/r2p	

24.	Two planets are orbiting a star in a distant galaxy. The first has a semimajor axis of 150 ´ 106 km, an eccentricity of 0.20, and a period of 1.0 Earth years. The second has a semimajor axis of 250 ´ 106 km, an eccentricity of 0.30, and a period of: 	
A)	0.46 Earth yr 	
B)	0.57 Earth yr 	
C)	1.4 Earth yr 	
D)	1.8 Earth yr 	
E)	2.2 Earth yr 	

25.	Assume that Earth is in circular orbit around the Sun with kinetic energy K and potential energy U, taken to be zero for infinite separation. Then, the relationship between K and U: 	
A)	is K = U 	
B)	is K = –U 	
C)	is K = U/2 	
D)	is K = –U/2 	
E)	depends on the radius of the orbit 	

26.	An artificial satellite of Earth nears the end of its life due to air resistance. While still in orbit: 	
A)	it moves faster as the orbit lowers 	
B)	it moves slower as the orbit lowers 	
C)	it slowly spirals away from Earth 	
D)	it moves slower in the same orbit but with a decreasing period 	
E)	it moves faster in the same orbit but with an increasing period 	

27.	Given the perihelion distance, aphelion distance, and speed at perihelion of a planet, which of the following CANNOT be calculated? 	
A)	the mass of the star 	
B)	the mass of the planet 	
C)	the speed of the planet at aphelion 	
D)	the period of orbit 	
E)	the semimajor axis of the orbit 	

28.	A planet in another solar system orbits a star with a mass of 4.0 ´ 1030 kg. At one point in its orbit it is 250 ´ 106 km from the star and is moving at 35 km/s. Take the universal gravitational constant to be 6.67 ´ 10–11 m2/s2 × kg and calculate the semimajor axis of the planet's orbit. The result is: 	
A)	79 ´ 106 km 	
B)	160 ´ 106 km 	
C)	240 ´ 106 km 	
D)	320 ´ 106 km 	
E)	590 ´ 106 km 	

Answer Key

1.	D	
2.	E	
3.	C	
4.	B	
5.	C	
6.	D	
7.	E	
8.	E	
9.	C	
10.	A	
11.	C	
12.	C	
13.	C	
14.	C	
15.	B	
16.	B	
17.	A	
18.	D	
19.	C	
20.	D	
21.	C	
22.	D	
23.	C	
24.	E	
25.	D	
26.	A	
27.	B	
28.	C