Asubstance that contains only one kind of matter is known as a (n)

Why is there friction between objects

Acharge of 8.4x10^-4 c moves at an angle of 35 degrees to a magnetic field that has a field strength of 6.7x10^-3 t. if the magnetic force is 3.5 x10 ^-2 n, how fast is the charge moving?

Asmall object with mass 0.200 kg swings back and forth on the lower end of a light rope that is 3.00 m long. the upper end of the rope is attached to the ceiling. as the object swings through its lowest position, where the rope is vertical, the speed of the object is 5.80 m/s. at this point in the motion, what is the tension in the rope? (use g = 9.80 m/s2.)