All of u what is the cause for moving object to speed up or down

Forces make things speed up (or accelerate). When a force pushes or pulls the object, the object will move in the direction of the force. The bigger the force, and the lighter the object, the greater the acceleration.

Explanation:

asthenosphere and convection

can be answered using momentum.

momentum = p

p1= mass1 * velocity1

p1 = p2

therefore

p1 = 6kg * 4m/s

p1 = 24kgm/s

p2=m2 * v2

24 kgm/s = 7kg * v2

v2 = 24 kgm/s / 7kg

v2= 3.42 m/s