Read the question again. Carefully. Might it be given?

You'll have to solve the given equation for the momentum, p. You are given the temperature T and the value of k. So only the mass is still unknown. What other information is given in this question that would allow you to determine (in the broadest sense: looking it up is also determining ) that mass?

Prob 1. Please check the units and orders of magntiude. 6.6e-34*2.57e15 = 1.6962e-18 J and 3.80*1.6e-19 = 6.08e-19.

Prob 2. "how do I get energy of pulse?" - that is given in the problem statement "intense pulse of light having an energy of 5960 J". The pulse width is superfluous with respect to energy, but would be a factor in a calculation of power.

1.) stupid mistake
2.) stupid mistake
3.) using p2=(3/2)(1.38e-23)(293)([2][8])=4.32e-20 with p=2.0797e-10 kg m/s can someone verify that it is correct...computer still says wrong but I don't know what else I am missing