Name two ways that friction is harmful and two ways that friction is when you are riding a bicycle.

Friction is harmful because if your riding and you suddenly stop the friction will make you keep going forward and you'll fall super hard on the concrete(my experience).You also lose your balance. Friction is helpful because it prevents you from hitting cars and pedestrians. 

Inaccuracy is a disadvantage

Answera tightly sealed house with an unvented water heater;