A person stands between two walls(A and B) and makes a loud sound by striking two metal rods together. He hears an echo from wall A after 4s, and hears a second echo from wall B after another 4s. Find the distance from the person to wall B. Speed of sound in air is 320m/s.

Acharge q experiences no net force at a particular point in space. which of the following situations described below must always be true? -there are no other charges nearby. -if there are other charges nearby, they must all have the same sign as q. -if there are other charges nearby, they must all have the opposite sign of q. -if there are other charges nearby, the total positive charge must equal the total negative charge. -none of the above

The path of a satellite orbiting the earth causes it to pass directly over two tracking stations a and b, which are 51 miles apart. when the satellite is on one side of the two stations, the angles of elevation at a and b are measured to be 87 degrees and 84 degrees, respectively. (a) how far is the satellite from station a? (b) how high is the satellite above the ground?

The standard cell potential (e°cell) for the reaction below is +0.63 v. the cell potential for this reaction is when the concentration of zn2+ = 1.0 m and the concentration of pb2+ = 2.0 x 10-4 m. pb2+(aq) + zn(s) > zn2+(aq) + pb(s)