Why are l waves not usually seen on a seisogram?

Aboy with a mass 25 kg climbs into a small tree. he sits on a branch that is 2.o m above to the ground.what is his gravitational potential energy above the ground?

The atoms in a nickel crystal vibrate as harmonic oscillators with an angular frequency of 2.3 × 1013 rad/s. the mass of a nickel atom is 9.75 × 10-26 kg. what is the difference in energy between adjacent vibrational energy levels of nickel? (h = 6.626 × 10-34 j • s, , 1 ev = 1.60 × 10-19 j)

Auniform brick of length 25 m is placed overthe edge of a horizontal surface with a maximum overhang of 12.5 m attained withouttipping. now two identical uniform bricks of length25 m are stacked over the edge of a horizontalsurface. what maximum overhang is possible forthe two bricks (without tipping)? answer in units of m.