Hi - Would someone check my method here please? Thank you 1. The problem statement, all variables and given/known data Two trolleys A and B, of mass 0.70kg and 0.80kg respectively, are on a horizontal track and held together by a compressed spring. When the spring is released the trolleys separate freely and A moves to the left with an initial velocity of 4.0m/s. Calculate: a) the initial velocity of A b) the energy initially stored in the spring 2. Relevant equations F=ma 3. The attempt at a solution a) (0.70x4.0)=(0.80xV) v=(0.70x4.0)/(0.80) v=3.5m/s b) This is a transfer of elastic potential energy to kinetic energy - Energy=1/2mv^2 mv=p(momentum) 1/2(0.70x4.0)^2 + 1/2(0.80x3.5)^2 =0.0392 + 3.92 =3.9592 J
This is good. You used conservation of momentum. Your mistake here was squaring mv, instead of just v. KE = 1/2mv^2, but you calculated 1/2(mv)^2. Not the same!