A child is sitting on the seat of a swing with ropes 10 m long. Their father pulls the swing back until the ropes make a 37o angle with the vertical and then releases the swing. If air resistance is neglected, what is the speed of the child at the bottom of the arc of the swing when the ropes are vertical

Explanation:

We shall apply conservation of mechanical energy law to solve the problem .

loss of height = L ( 1 -  cos 37 ) where L is length of rope

loss of potential energy at the bottom = gain of kinetic energy .

mg L ( 1 - cos 37 ) = 1/2 m v² where v is velocity at the bottom

v² = 2 L g ( 1 - cos 37 )

= 2 x 10 x 9.8 ( 1 - cos 37 )

= 39.46

v = 6.28 m /s

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.