WASHINGTON—President Barack Obama is reaching out to an online audience, answering questions that range from gun violence to anachronism of pennies, from minimum wage to deportations.

Obama is participating in a Google+ Hangout, answering questions submitted online as part of a post-State of the Union outreach to promote his initiatives.

Obama defended his proposals to ban certain weapons and bullet magazines and expand background checks on gun buyers. He said that, even with the Second Amendment, Americans can't go to a store to purchase grenade launchers.

Asked why the government hasn't done away with the penny, Obama said he didn't know, but suspected there was an emotional attachment to the coin. He said the penny was a metaphor for how the government sometimes clings to things that do not work.