ОГН_10_grade_Newton’s Universal Law of Gravitationl_Formative assessment test

Formative assessment test.

Name……………………………………………………………..class………………………………………………………..Date…………………….

You can use these constants:

G = 6.67 ´ 10^-11 N m² kg^-2 , mass of the Earth = 6.0 ´ 10²⁴ kg

Radius of the Earth, R_E = 6.4 ´ 10⁶ m,    gravitational field strength close to the surface of the Earth is 9.8 N kg^-1

1.       Gravitational field strength at a point may be defined as

A.      the force on a small mass placed at the point.

B.      the force per unit mass on a small mass placed at the point.

C.      the work done to move unit mass from infinity to the point.

D.      the work done per unit mass to move a small mass from infinity to the point.

2.       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

   3. During a solar eclipse, the Moon, Earth, and Sun all lie on the same line, with the Moon between Earth and the Sun. The mass of the sun M_S = 1.991 x 10³⁰ Kg , mass of moon M_M = 7.36 x 10²² Kg. The distance between the sun and the moon is 1.496 x 10¹¹ m while the distance between the moon and the earth is 3.81 x 10¹⁰ m

(a) What force is exerted on the Moon by the Sun?

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(b) What force is exerted on the Moon by Earth?

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(c) What force is exerted on Earth by the Sun?

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    4. This question is about gravitational fields.

(a)     Define gravitational field strength.

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 (b)    The gravitational field strength at the surface of Jupiter is 25 N kg–1 and the radius of Jupiter is 7.1 ´ 107 m.

(i)      Derive an expression for the gravitational field strength at the surface of a planet in terms of its mass M, its radius R and the gravitational constant G.

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(ii)     Use your expression in (b)(i) above to estimate the mass of Jupiter.

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Answers

1.    B

2.     

3.     

4. (a)     the force exerted per unit mass;

on a point (small) mass;                                                                                       

 (b)    (i)      use of  and  combine to get                         

(ii)      substitute to get M = 1.9 ´ 1027 kg;