An object stays at rest until what happens to it?
a. inertia releases it.
b. gravity overcomes friction.
c. friction builds up and moves the object.
d. an outside or unbalanced force acts upon the object.

Wo audio speakers are placed on a vertical rail. speaker a is placed at head-level while speaker b is place at some variable height, \delta yδy, above speaker a. both speakers receive simultaneous input from a sine-wave generator so the speakers each produce a pure sinusoidal sound wave with a wavelength of 0.531 meters. calculate the lowest height that speaker b can be placed above speaker a to produce a minimum of sound heard by person standing \delta x = 7.86δx=7.86 meters directly in front of speaker a.

Spend time observing or thinking about events that involve matter and energy. which events can you explain? which events can’t you explain?

Ais not a compound machine. a. bolt b. shovel c. handcart (dolly) d. see-saw (teeter totter)