An opera singer breaks a crystal glass with her voice. which best explains why this occurs? 1. the pitch of her voice matches the pitch of the glass. 2. the amplitude of her voice heats the glass until it breaks. 3. the intensity of her voice produces a standing wave in the glass. 4. the frequency of her voice matches the natural frequency of the glass.

What property is a characteristic of a substance that can be observed and does not change the identity of the substance

A150 w lamp emits light of wavelength 590 nm uniformly in all directions. what is the photon flux (photons per unit area per unit time) on a small screen at a distance 2.3 m from the lamp? assume the photons are uniformly distributed over the surface of a sphere of radius 2.3 m.

As part of your daily workout, you lie on your back and push with your feet against a platform attached to two stiff springs arranged side by side so that they are parallel to each other. when you push the platform, you compress the springs. you do an amount of work of 79.0 j when you compress the springs a distance of 0.230 m from their uncompressed length. (a) what magnitude of force must you apply to hold the platform in this position? (b)how much additional work must you do to move the platform a distance 0.230 m farther? (c) what maximum force must you apply to move the platform a distance 0.230 m farther?