What are differences between Piaget and Erikson's work? Both study different aspects of human development.
Each has a different number of stages in his theories.
Each has different ideas about how people progress through stages.
all of the above.

all of the above

Explanation:

if the thermos has a vacuum innner, then heat through conv currents and conduction are reduced = vacuum flask

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.