1. What are the two (2) classes of matter? A. Atom and molecule
B. Element and compound
C. Plant and animal cells
D. Substance and mixture
2. Which is true regarding water?
A. Compound of element
B. Element of gases
C. Mixture of
gases
D. Substances of gases
3. What is the difference between a substance and a mixture?
A. Substance can be separated while mixture cannot be separated.
B. Substance has many components while mixture has one only.
C. Substance is heterogeneous while mixture is homogeneous.
D. Substance is pure while mixture is impure.

An implanted pacemaker supplies the heart with 72 pulses per minute, each pulse providing 6.0 v for 0.65 ms. the resistance of the heart muscle between the pacemaker’s electrodes is 550 ω. find (a) the current that flows during a pulse, (b) the energy delivered in one pulse, and (c) the average power supplied by the pacemaker.

This problem has been solved! see the answera non-uniform fire escape ladder is 6.0m long whenextended to the icy alley below. it is held at the top by africtionless pivot, and there is neglibible frictional force fromthe icy surface at the bottom. the ladder weighs 250n, and it'scenter of gravity is 2.0m along the ladder from the bottom. amother and child of total weight 750n are on the ladder 1.5m fromthe pivot. the ladder makes an angle θ with the horizontal.find the magnitude and direction ofa) the force exerted by the icy alley on the ladderb) the force exerted by the ladder on the pivotc) do your answers in part a and b depend on the angle?

At what time will the interfering waves have an amplitudeof zero?