What is an electron?

Particle or wave? Here is a quote from a textbook describing what an electron “is”.

1. Giancoli, Physics 5th edition page 837. We might ask ourselves: "What is an electron?" The early experiments of J. J. Thomson indicated a glow in a tube that moved when a magnetic field was applied. The results of these and other experiments were best interpreted as being caused by tiny negatively charged particles which we now call electrons. No one, however has actually seen an electron directly. The drawings we sometimes make of electrons as tiny spheres with a negative charge on them are merely convenient pictures (now recognized to be inaccurate). Again we must rely on experimental results, some of which are best interpreted using a particle model and others the wave model. These models are mere pictures that we use to extrapolate from the macroscopic world to the tiny microscopic world of the atom. And there is no reason to expect that these models somehow reflect the reality of an electron. We thus use a wave or a particle model (whichever works best in the situation) so that we can talk about what is happening. But we shouldn't be led to believe that an electron is a wave or a particle. Instead, we could say that an electron is the set of its properties that we can measure. Bertrand Russell said it well when he wrote that an electron is a "logical construction".

IB Physics Challenging Mechanics Questions

A tutorial sheet of difficult mechanics questions is given below.

1. A ball rolls horizontally from a table of height 2.0 m. On collision with the smooth horizontal floor the kinetic energy of the ball is reduced by one-half. At what speed does the ball leave the table if it strikes a vertical wall 1.0 m from the table at a height of 1/3 m above the floor? (0.75 m/s, 1.20 m/s, 1.92 m/s)
2. Adapted from the Moscow Physics Problems (MPP) 1986-2005, 1.15. A projectile moves horizontally at 10.0 ms^-1 at a height above the ground of 30.0 m. When it is 25.0 m from a vertical wall it explodes and disintegrates into many fragments flying in all directions and all having an initial speed of 20.0 ms^-1 relative to the projectile. Find the area on the surface of the wall that will be hit by the debris. Assume that fragments hitting the ground do not bounce and ignore air resistance. ( 4673.91 m² , x axis along initial direction of motion, max height on wall z = 50.19 m, hits wall at ground level at y = 61.75 m, g = 9.81 m s^-2 )
3. In the previous question the wall is not present. Determine the area on the ground that can be struck by debris from the explosion. (1.8007 ha, on x axis debris lands 104.14 m ahead and 28.73 m behind explosion point)
4. In question 3 determine the time interval during which debris is hitting the ground. ( 4.08 s )
5. In question 3 the explosion occurs at a vertical height of 30.0 m over an inclined plane of angle of elevation 20°. Determine the area on the incline on which debris lands. ( 1.1801 ha, debris lands a maximum 70.92 m ahead and 46.38 m behind, on the incline measured from the perpendicular to the plane through the explosion point )