Answer:
<em>High-speed rail in China is officially defined as "newly-built passenger-dedicated rail lines designed for electrical multiple unit (EMU) train sets traveling at not less than 250 km/h (155 mph) (including lines with reserved capacity for upgrade to the 250 km/h standard) <u>on which initial service operate at not less ...</u></em>
Explanation:
Many would know it as a reaction force. Reaction force is the force by the surface on the object perpendicular to it's motion. So if we apply force on the sliding block perpendicular to it's direction of motion, friction will increase. ... That force is proportional to the velocity with which it is moving.
Answer:
The crystal structure of topaz is the Orthorhombic crystal system
Explanation:
Because it is a Dipyramid and the Orthorhombic crystal system consists of prisms and dypiramids
Answer:
a= (-g) from the moment the ball is thrown, until it stops in the air.
a = (0) when the ball stops in the air.
a = (g) since the ball starts to fall.
Explanation:
The acceleration is <em>(-g)</em> <em>from the moment the ball is thrown, until it stops in the air</em> because the movement goes in the opposite direction to the force of gravity. In the instant <em>when the ball stops in the air the acceleration is </em><em>(0)</em> because it temporarily stops moving. Then, <em>since the ball starts to fall, the acceleration is </em><em>(g)</em><em> </em>because the movement goes in the same direction of the force of gravity