Predict/Calculate In the following, assume that lightbulbs radiate uniformly in all directions and that 5 0% of their power is converted to light (a) Find the average intensity of light at a point 2 0 m from a 120-W red lightbulb (λ = 710 nm). (b) Is the average intensity 2.0 m from a 120-W blue lightbulb (λ = 480 nm) greater than less than, or the same as the intensity found in part (a)? Explain. (c) Calculate the average intensity for part (b).
Predict/Calculate In the following, assume that lightbulbs radiate uniformly in all directions and that 5 0% of their power is converted to light (a) Find the average intensity of light at a point 2 0 m from a 120-W red lightbulb (λ = 710 nm). (b) Is the average intensity 2.0 m from a 120-W blue lightbulb (λ = 480 nm) greater than less than, or the same as the intensity found in part (a)? Explain. (c) Calculate the average intensity for part (b).
Predict/Calculate In the following, assume that lightbulbs radiate uniformly in all directions and that 5 0% of their power is converted to light (a) Find the average intensity of light at a point 2 0 m from a 120-W red lightbulb (λ = 710 nm). (b) Is the average intensity 2.0 m from a 120-W blue lightbulb (λ = 480 nm) greater than less than, or the same as the intensity found in part (a)? Explain. (c) Calculate the average intensity for part (b).
Study of body parts and their functions. In this combined field of study, anatomy refers to studying the body structure of organisms, whereas physiology refers to their function.
A skateboarder with his board can be modeled as a particle of mass 80.0 kg, located at his center of mass. As shown in the figure below, the skateboarder starts from rest in a crouching position at one lip of a half-pipe (point). On his descent, the skateboarder moves without friction so
that his center of mass moves through one quarter of a circle of radius 6.20 m.
i
(a) Find his speed at the bottom of the half-pipe (point Ⓡ).
m/s
(b) Immediately after passing point Ⓑ, he stands up and raises his arms, lifting his center of mass and essentially "pumping" energy into the system. Next, the skateboarder glides upward with his center of mass moving in a quarter circle of radius 5.71 m, reaching point D. As he
passes through point ①, the speed of the skateboarder is 5.37 m/s. How much chemical potential energy in the body of the skateboarder was converted to mechanical energy when he stood up at point Ⓑ?
]
(c) How high above point ① does he rise?
m
A 31.0-kg child on a 3.00-m-long swing is released from rest when the ropes of the swing make an angle of 29.0° with the vertical.
(a) Neglecting friction, find the child's speed at the lowest position.
m/s
(b) If the actual speed of the child at the lowest position is 2.40 m/s, what is the mechanical energy lost due to friction?
]
Chapter 25 Solutions
Modified Mastering Physics with Pearson eText -- Access Card -- for Physics (18-Weeks)
Microbiology with Diseases by Body System (5th Edition)
Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.