Using the information from example 28.1, how much fainter an object will you have to be able to measure in order to include the same kinds of galaxies in your second survey? remember that the brightness of an object varies as the inverse square of the distance.

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.

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it

the components of a vector are the parts of the vectors that are to each other.

b perpendicular