逸速く[ichihayaku] promptly
音速[onsoku] speed of sound
加速[kasoku] acceleration
加速運動[kasokuundou] accelerated motion
加速度[kasokudo] acceleration

快速[kaisoku] high speed
快速電車[kaisokudensha] high-speed train
角速度[kakusokudo] angular velocity
急速[kyuusoku] rapid (e.g. progress)
減速[gensoku] deceleration

才槌[saizuchi] small wooden mallet
才槌頭[saizuchiatama] head like a hammer
相槌[aizuchi] sounds given during a conversation to indicate comprehension
相槌を打つ[aizuchiwoutsu] to throw in appropriate words in a conversation
金槌頭[kanazuchiatama] hard-headed

小槌[kozuchi] (small) mallet
打ち出の小槌[uchidenokozuchi] figurative magic wand
鉄槌[kanazuchi] (iron) hammer
木槌[kizuchi] wooden hammer