Answer:
When you rub a balloon on your head, electrons move from the atoms and molecules in your hair onto the balloon. Electrons have a negative charge, so the balloon becomes negatively charged, and your hair is left with a positive charge.
Explanation:
I’m not Vietnamese but I think your asking for this, for people who understand Vietnamese pls help them :d
I'll assume that the chair has four legs.
Since the chair weights 3.7 kg by itself, it will weigh (79+3.7)=82.7 kg with the person sitting on it. And each of the chair's legs will take about (82.7/4)=20.675 kg.
Each leg touches the floor in a circle with 1.3cm diameter. The area of that circle is about (3.14*(1.3/2)^2)=1.327 cm^2.
Pressure is measured by force per area. So, the pressure from each leg is about 20.675kg / 1.327cm^2. That simplifies to 15.58 kg/cm^2.
Answer:
D) Vertically.
Explanation:
A free body diagram is used to represent all the forces acting in a body. forces like, the force of gravity as a result of the gravitational interaction between the object and the Earth (W), the frictional force opposite to the movement of the object (
), the normal force due to the plane and the object (N) and the force applied to start the movement in a particular direction (F).
As is show in the free body diagram of the system, W, which is the weight of the body as a consequence of the gravitational force, is at an angle 
below the inclined plane. that angle between the plane and the x axis is the same that the one of the inclined plane with respect to the horizontal, Since its sides are perpendicular.
Notice how W goes always in the direction to the center of mass of Earth in a vertical path (For comparison see figure (a) and (b)).
