The mass is just sitting there motionless. There is no acceleration and it is in equilibrium. What does this mean? This means that the net force in the y-direction (vertical direction) must be zero. I ...

For those of you who take sandcastle building very seriously, listen up: engineers now say you can trust a very simple equation to calculate the force required to push a shovel -- and any other ...

For those of you who take sandcastle building very seriously, listen up: MIT engineers now say you can trust a very simple equation to calculate the force required to push a shovel -- and any other ...