A 1.33 kg mass is attached to a spring (k = 40 N/m) on a level surface without friction. It is pulled the right 0.4 m (a) and released. When it reaches the equilibrium position ((b), x=0), how fast is it traveling?

Can someone explain to me how to do this problem ?

The intensity of a polarized electromagnetic wave is 12 w/m^2. part a) what will be the intensity after passing through a polarizing filter whose axis makes the angle θ=0∘ with the plane of polarization? part b) what will be the intensity after passing through a polarizing filter whose axis makes the angle θ=30∘ with the plane of polarization? part c) what will be the intensity after passing through a polarizing filter whose axis makes the angle θ=45∘ with the plane of polarization? part d) what will be the intensity after passing through a polarizing filter whose axis makes the angle θ=60∘ with the plane of polarization? part e) what will be the intensity after passing through a polarizing filter whose axis makes the angle θ=90∘ with the plane of polarization?

Which transition by an electron will release the greatest amount of energy? oa ob oc od