John is pushing a wheelbarrow filled with sand on a building site. The total mass of the wheelbarrow and its contents is 30kg. When he applies a force of 20N, the wheelbarrow moves forward at a constant speed. What is the magnitude of the friction between the wheels and the ground?Explain your answer.(20N)​

The particles that are found in the nucleus of an atom are

Efficiency is the ratio of to for a system a)power in to power in b)power in to power out c) power out to power out d) power out to power in

Abaseball is thrown from the outfield toward the catcher. when the ball reaches its highest point, which statement is true? (a)its velocity is not zero, but its acceleration is zero. (b) its velocity and its acceleration are both zero. (c) its velocity is perpendicular to its acceleration. (d) its acceleration depends on the angle at which the ball was thrown. (e) none of the above statements are true.