In the United States, the average age for a girl to get her first period is 12. This does not mean that all girls start at the same age. A girl can start her period anytime between the ages of 8 and 15. Most of the time, the first period starts about 2 years after breasts first start to develop. If a girl has not had her first period by age 15, or if it has been more than 2 to 3 years since breast growth started, she should see a doctor.
Cancel Save! You can build a balance beam out long pieces of wood covered with thick cloth, or sand it smooth so you don't get a splinter. A piece of wood laid on the ground is not a balance beam. Balance beams are 10 cm wide, 500 cm long, and usually 124 cm off the ground. Post Your Project.
In weighing an object directly on the pan, you must still make two weighings. The first of these is to weigh the empty pan! This must be set to read 0.00 g. The triple beam balance has a little knob under the pan which you screw in or out to set the empty balance to read exactly 0.00 g. So, in weighing an object directly on the pan, you must first Zero the balance. Only if the balance is properly zeroed, will it weigh the object correctly.