PHY_10_15_V1_DM_The law of universal gravitation

Formative assessment

1.       A spherical planet of uniform density has three times the mass of the Earth and twice the average radius. The magnitude of the gravitational field strength at the surface of the Earth is g.
What is the gravitational field strength at the surface of the planet?

A.      6 g

B.     

C.     

D.     

(Total 1 mark)

2.       A spacecraft travels away from Earth in a straight line with its motors shut down. At one instant the speed of the spacecraft is 5.4 km s–1. After a time of 600 s, the speed is 5.1 km s–1. The average gravitational field strength acting on the spacecraft during this time interval is

A.      5.0 × 10–4 N kg–1

B.      3.0 × 10–2 N kg–1

C.      5.0 × 10–1 N kg–1

D.      30 N kg–1

(Total 1 mark)

3.       The weight of an object of mass 1 kg at the surface of Mars is about 4 N. The radius of Mars is about half the radius of Earth. Which of the following is the best estimate of the ratio below?

A.      0.1

B.      0.2

C.      5

D.      10

(Total 1 mark)

 4.      Which of the following is true about gravitational field lines?

A.      They are always tangential to equipotential surfaces.

B.      They are always perpendicular to equipotential surfaces.

C.      They can be both tangential or perpendicular to equipotential surfaces.

D.      They can have any angle to the equipotential surfaces.

(Total 1 mark)

5.       Which of the following is true about the gravitational potential V due to a point mass at a distance r from the point mass?

A.      V  and always positive

B.      V  and always negative

C.      V  and always positive

D.      V  and always positive

(Total 1 mark)

Free response questions

Additional problem for differentiation

Mark scheme of FA

1.       C

[1]

2.       C

[1]

3.       A

[1]

4.       B

[1]

5.       B

Answers to additional problem