Questions and Answers of Inquiry into Physics

Initially stationary, a train has a constant acceleration of 0.5 m/s2.(a) What is its speed after 15 s?(b) What is the total time required for the train to reach a speed of 25 m/s?
If a ball is thrown straight up into the air, what is its acceleration as it moves upward? What is its acceleration when it reaches its highest point and is stopped at an instant?
In Figure 1.19, arrows show the directions of the velocity and the acceleration of a ball moving in a circle. Make a similar sketch showing these directions for a car Figure 1.19(a) speeding up
The following are speeds and headings displayed on a GPS receiver. (Heading gives the direction of motion based on north 5 0°, east 5 90°, south 5 180°, etc.) In each case, indicate whether the
A child sits on the edge of a spinning merry-go-round that has a radius of 1.5 m. The child’s speed is 2 m/s. What is the child’s acceleration?
As a car goes around a curve, the driver increases its speed. This means the car has two accelerations. What are the directions of these two accelerations?
During 200-meter and 400-meter races, runners must stay in lanes as they go around a curved part of the track. If runners in two different lanes have exactly the same speed, will they also have
As a baseball is being thrown, it goes from 0 to 40 m/s in 0.15 s.(a) What is the acceleration of the baseball?(b) What is the acceleration in g’s?
What is centripetal acceleration? What is the direction of the centripetal acceleration of a car going around a curve?
Using concepts and physical quantities discussed in this chapter, explain why it is usually safe for a person standing on the seat of a chair to jump horizontally and land on the floor, but not for a
The graph inFigure 1.38 shows the distance versus time for an elevator as it moves up and down in a building.Compute the elevator€™s velocity at the times marked a, b, and c. 32 28 24 20 16
How does the velocity of a freely falling body change with time? How does the distance it has fallen change? How about the acceleration?
As a stop light changes from red to green, a car starts to cross through the intersection. An instant before it begins to move, its velocity is zero. Must its acceleration at that time also be zero.
A long-distance runner has an average speed of 4 m/s during a race. How far does the runner travel in 20 min?
What is the relationship between velocity and acceleration?
A basketball player shoots a free throw. Make a sketch showing the basketball’s velocity just after the ball leaves the player’s hands. Draw in two components of this velocity, one horizontal and
On a day when the wind is blowing toward the south at 3 m/s, a runner jogs west at 4 m/s. What is the velocity (speed and direction) of the air relative to the runner?
A swimmer heads for the opposite bank of a river. Make a sketch showing the swimmer’s two velocities and the resultant velocity.
Can the resultant of two velocities have zero magnitude? If so, give an example.
The Moon is about 3.8 × 108 m from Earth. Traveling at the speed of light, 3.0 × 108 m/s, how long does it take a laser beam to go from Earth to the Moon and back again? The same physics was
What is “vector addition” and how is it done?
Air Force Col. John P. Stapp was a pioneer in the study of the effects of large, rapid accelerations and decelerations on humans, as well as one of the early designers and advocates for
A ball thrown at a brick wall bounces directly back with the same speed it had when it struck the wall. Has the velocity of the ball changed? Explain.
A race car starts from rest on a circular track with radius 100m and begins to increase its speed by 5 m/s each second. At what point in time is the car’s vector acceleration directed 45° away
At the 2006 Winter Olympics in Torino, Italy, U.S. speed skater Apolo Ohno took the gold medal for the 500-m sprint by completing the course in 41.935 s. What was his average speed for this event?
What is the distinction between speed and velocity? Describe a situation in which an object’s speed is constant but its velocity is not.
For an object starting at rest with a constant acceleration, derive the equation that relates its speed to the distance it has traveled. In other words, eliminate time in the two equations relating d
List the physical quantities identified in this chapter. From which of the fundamental physical quantities is each derived? Which of them are vectors, and which are scalars?
The quartz crystal used in an electric watch vibrates with a frequency of 32,768 Hz. What is the period of the crystal’s motion?
When an object is thrown straight upward, gravity causes it to decelerate at a rate of 1 g —its speed decreases 9.8 m/s or 22 mph each second. (a) Explain how we can use the equations, tables,
A wind is blowing from the north (the air is moving toward the south). When a person is walking toward the north, is the relative speed of the wind that the person senses greater than, the same as,
A spacecraft lands on a newly discovered planet orbiting the star 51 Pegasi. To measure the acceleration from gravity on the planet, an astronaut drops a rock from a height of 2 m. A precision timer
What are the “basic” or “fundamental” physical quantities? Why are they called that?
A sports car is advertised to have a maximum cornering acceleration of 0.85 g.(a) What is the maximum speed that the car can go around a curve with a 100-m radius?(b) What is its maximum speed for a
One mile is equal to 1,609 m. Express this distance in kilometers and in centimeters.
A pendulum clock is taken to a repair shop. Its pendulum is replaced by a shorter one that oscillates with a smaller period than the original. What effect, if any, does this have on how the clock
A car is stopped at a red light. When the light turns green, the car begins to accelerate with a constant acceleration of 4.0 m/s2. Just as the car starts moving, it is passed by a small truck
Explain what a “derived unit” of measure is.
The Moon’s mass is 7.35 × 1022 kg, and it moves in a nearly circular orbit with radius 3.84 × 108 m. The period of its motion is 27.3 days. Use this information to determine the Moon’s (a)
Express your height in(a) Meters (b) Centimeters.
Two rectangular rugs are on display in a showroom. If one rug is twice as long as the other, does this necessarily mean that its area is also twice as large as that of the second? Explain.
Most cars can decrease their speed much more rapidly than they can increase it. What factors contribute to cause this?
Consider Concept Map 1.1, which provides an overview of motion. Review Sections 1.2 and 1.3 and make a list of at least five additional concepts you could add to the map. Now consider where to place

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