An blank is an object that allows only some electrons to go through it

Not all tiles will be usedidentify the element present in each star based on the gaps observed in wavelengths of its light refer to this table containing absorption wavelengths (in nm) of several different elements the table ishelium 447, 502 ,587 ,668carbon 427 ,515, 600 ,678sulfur 425, 565, 639, 675xenon 484, 590, 687calcium 429 ,527, 593, 645silver 421 ,521, 662

Eddy whose mass is 55kg climbs up the 1.50 meter high stairs in 2s.calculate eddy’s power rating

Assume you measured the mass of the cart to be (500 ± 1) g and the mass of the additional mass you put on the cart to be (500 ± 1) g as well. since the scale you are using in the lab cannot measure objects heavier than 600g you will have to sum up individual pieces and propagate the error. so what would be the mass and the standard error of the cart and the mass