If a machine exerts a force of 250N on an object and no work is done, what must have occurred? A) The machine has broken

B) The object has not moved

C) The object has gained momentum.

D) The object has moved, but then stopped

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

read more on -

according to jean piaget, in what stage of cognitive development are children able to understand conservation task?

b. preoperational

just took it