heat
Convection, and thermal expansion.
Magma is propelled to the surface by temperature differences, which cause convection currents. The temperature differences result from radioactive elements within the mantle.
Thrust
Force is porportional to area. A purely (theoretical) flat surface will have equal amounts of force applied to every point in contact, provided that the object weighs the same in each point.
force of friction
Pressure.
voalcano erupt
no... if a force is not great enough to overcome the static friction then the object will not move also if the force is directly perpendicular to the surface, provided its solid, the object is on it wont move
The brain is soft tissue enclosed in hard bone, the skull. When the head is hit with force, it cuases the brain to hit the skull causing a "bruise' or concussion.
No. Frictional force is independant of surface area.
If that force is not perpendicular to the surface, then there is a component of the force that's parallel to the surface. That component would move fluid around, until there were no longer any force parallel to the surface ... and the whole force would again be perpendicular to the surface.
Close to Earth's surface, this force is about 9.8 newton for every kilogram of mass.