What is a antiparticle?

Why are they difficult to detect.

An antiparticle has the same mass and dimension as its corresponding particles but opposite charge.  For example, a proton has  a mass of apprx. 1amu and a charge of +1.6e-19C.  The antiproton has a mass of 1amu but a charge of -1.6e-19C.

They are extremely rare though because if they appear they quickly meet up with their equivalent particle then annihilate each other to produce energy in the form of high energy photons (gamma rays)

A particle which cannot be split or broken down any further. 

At present we think particles like the electron and the quark are fundamental particles.

What are the three fundamental forces?

Describe their properties.

Gravitational force - acts between masses and is only attractive, weakest force (10e36 times wekaer than the electromagnetic force) acts over distance, proportional to 1/r2.

Electromagnetic force - acts between charges, attracts and repels, acts over any distance, proportional to 1/r2

Strong force - acts betwen nucleons, attractive and repulsive(if nucleons get too close), 100 times stroner than electromagnetic force.  Acts over very small distances of less than 10e-14. 

Hadrons - Made up of two or three quarks.  Influenced by the strong force.

Leptons - Are fundamental.  Are not influenced by the strong force.