Q: What is the value of the gravitational constant $$G in SI $$units?

$$G = 6.67 \times 10$$^{-11}$$ \ \mathrm{N \cdot m^2$ / kg^2$}$$

Question 1

Which equation represents Newton's law of universal gravitation for two masses $$m_1$$ and $$m_2$$ separated by a distance $$r$$?

Accepted Answer

$$F = G \frac{m_1$ m_2$}{r^2$}$$

Question 2

What is the value of the gravitational constant $$G in SI $$units?

Accepted Answer

$$G = 6.67 	imes 10$$^{-11}$$ \ \mathrm{N \cdot m^2$ / kg^2$}$$

Question 3

A space probe of mass $$m_p = 120 \ \mathrm{kg} is $$launched from Earth and is exactly halfway between the Earth and the Sun. Which exerts the stronger gravitational force on the probe?

Accepted Answer

The Sun, because it is much more massive than the Earth.

Question 4

If the separation between two masses is doubled, by what factor does the gravitational force between them change?

Accepted Answer

The force decreases by a factor of 4.

Question 5

What is the formula for the gravitational weight $$F_g of an $$object of mass $$m$$ near the surface of the Earth?

Accepted Answer

$$F_g = mg$$

Question 6

Which of the following best describes the direction of the gravitational force acting on the Earth due to the Sun as the Earth orbits the Sun?

Accepted Answer

It always points directly toward the Sun.

Question 7

Newton's third law states that the gravitational force exerted by the Earth on the Sun is:

Accepted Answer

Equal in magnitude and opposite in direction to the force exerted by the Sun on the Earth.

Question 8

A car travels around a curve of radius $$r at $$constant speed $$v. $$What is the required centripetal acceleration?

Accepted Answer

$$a_c = \frac{v^2$}{r}$$

Question 9

If the mass of the Earth is reduced to one-half its normal value, what happens to the gravitational force between the Earth and the Sun?

Accepted Answer

The force is reduced by a factor of 2.

Question 10

What is the SI unit for gravitational force?

Accepted Answer

Newton ($$\mathrm{N})$$

Question 11

Which equation accurately describes the normal force $$n$$ acting on a car moving in a circle on a flat surface, assuming no vertical acceleration?

Accepted Answer

$$n = mg$$

Question 12

A space probe is halfway between the Earth and the Sun. Ignoring other objects, what is the net direction of the gravitational force acting on the probe?

Accepted Answer

Toward the Sun, because the Sun is much more massive.

Question 13

What is the value of the gravitational free-fall acceleration constant $$g$$ near the surface of the Earth?

Accepted Answer

$$g = 9.80 \ \mathrm{m/s^2$}$$

Question 14

If the separation distance between two masses is increased by a factor of 4, by what factor does the gravitational force decrease?

Accepted Answer

The force decreases by a factor of 16.

Question 15

Which of the following is NOT a correct application of Newton's law of universal gravitation?

Accepted Answer

Calculating the weight of an object near the surface of the Earth using $$F_g = mg.$$

Question 16

A car is moving in a circle of radius $$r at $$speed $$v. $$What is the net force required to keep it moving in a circle?

Accepted Answer

$$F = m \frac{v^2$}{r}$$

Question 17

Which of the following statements about gravitational force is correct?

Accepted Answer

Gravitational force is always attractive.

Question 18

If the mass of the Sun is reduced to one-fourth its normal value, what happens to the gravitational force between the Earth and the Sun?

Accepted Answer

The force is reduced by a factor of 4.

Question 19

Which equation is used to calculate the gravitational force between the Earth and a space probe of mass $$m_p at a $$distance $$r$$ from the Earth's center?

Accepted Answer

$$F = G \frac{m_{	ext{earth}} m_p}{r^2$}$$

Study Guide: Circular Motion, Gravity, Work and Energy

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