7.A hiker shouts toward a vertical cliff that is 685 m away. The echo is heard 4.0 s later. (a) What is the sound wave’s speed (v)? (b) The wavelength (λ) of the sound is 0.75 m. What is the wave’s frequency (f)? (c) What is the wave’s period (T)?

A10.0 kg cart and a 15kg cart are locked together with a compressed spring between them. they are then released so that the spring pushes the two carts apart. the 10.0 kg cart is moving at 4.5 m/s afterward. how fast is the 15kg cart moving? 3.0 m/s 2.0 m/s 4.5 m/s 5.0 m/s

Which units can be used to measure length or distance? check all that apply. gram meter kilometer liter inch

In a system, when potential energy decreases, then entropy also decreases. true false