A surveyor wishes to measure the distance between two points on either side of a river, as illustrated in Figure 1.29. She measures the distance AB to be 290 m and the angle at B to be 30°. What is the distance between the two points?

Enter a number.

1 m

Figure 1.29

Use Newton's law of gravity to calculate the force of gravity between you and Earth. Convert your answer, which will be in Newtons, to pounds using the conversion 4.45 N equals one pound. (Assume that your mass is 45 kg.)

Enter a number.

1 N

Enter a number.

2 lbs
What do you normally call this force?

Answer is not case sensitive.

3

If the mass of an object is doubled, its gravitational force is quadrupled.

If Earth were completely blanketed with clouds and we couldn't see the sky, could we learn about the realm beyond the clouds?
1
What forms of radiation might be received?

Astronomers on Earth are observing the occultation of a star by Uranus and its rings (see Figure 13.18). It so happens that the event is occurring when Uranus is at opposition, and the center of the planet appears to pass directly across the star. Assuming circular planetary orbits and, for simplicity, taking the rings to be face-on, calculate the following.

Figure 13.18

(a) How long the 90 km wide Epsilon ring takes to cross the line of sight?

Enter a number.

1 seconds
(b) The time interval between the passage of the Alpha ring and that of the Epsilon ring. (Hint: The apparent motion of Uranus is due to a combination of both the planet's own motion and Earth's motion in their respective orbits around the Sun.)

Enter a number.

2 s