Which of the following are thought to be rapidly rotating neutron stars with intense magnetic fields? choose one answer. a. pulsarsb. white dwarfsc. black holesd. flare starse. accretion disks

A pulsar is a neutron star that emits very intense electromagnetic radiation at short and periodic intervals ( rotating really fast) due to its intense magnetic field that induces this emission.  

Nevertheless, it is important to note that all pulsars are neutron stars, but not all neutron stars are pulsars.

Let's clarify:

A neutron star, is the name given to the remains of a supernova. In itself it is the result of the gravitational collapse of a massive supergiant star after exhausting the fuel in its core.  

Neutron stars have a small size for their very high density and they rotate at a huge speed.  

However, the way to know that a pulsar is a neutron star is because of its high rotating speed.  

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.