# Hope

Topics: Light, Standing wave, Electromagnetic radiation Pages: 4 (1049 words) Published: July 31, 2014
﻿Chapter 7

1. A woman passes through a revolving door with a tangential speed of 1.8 m/s. If she is 0.80 m from the center of the door, what is the door’s angular speed?

1. A girl sits on a tire that is attached to an overhanging tree limb by a rope. The girl’s father pushes her so that her centripetal acceleration is 3.0 m/s2. If the length of the rope is 2.1 m, what is the girl’s tangential speed?

1. A girl sits in a tire that is attached to an overhanging tree limb by a rope 2.10 m in length. The girl’s father pushes her with a tangential speed of 2.50 m/s. If the magnitude of the force that maintains her circular motion is 88.0 N, what is the girl’s mass?

3. Find the magnitude of the gravitational force a 67.5 kg person would experience while standing on the surface of each of the following planets: PRACTICE 7I
Gravitational force
“Planet” m r
Earth 5.98 1024 kg 6.37 106 m
Mars 6.34 1023 kg 3.43 106 m
Pluto 5 1023 kg 4 105 m
1. A roller coaster moves through a vertical loop at a constant speed and suspends its passengers upside down. In what direction is the force that causes the coaster and its passengers to move in a circle? What provides this force?

37. A roller-coaster car speeds down a hill past point A and then rolls up a hill past point B, as shown in Figure 7-17.
a. The car has a speed of 20.0 m/s at point A. If the track exerts a force on the car of 2.06 104 N at this point, what is the mass of the car?

b. What is the maximum speed the car can have at point B for the gravitational force to hold it on the track?

CHAPTER 25
1. Calculate the total binding energy of 20 10Ne and 4020Ca.

2. Oxygen has several isotopes. What do these isotopes have in common? How do they differ?

3. Of atomic number, mass number, and neutron number, which are the same for each isotope of an element, and which are different?

1. Complete this radioactive-decay formula: 125B  0-1e

2....