If Uraraka can turn weightless anything she touches, why she didnt use her quirk to get out of the debris in the episode where Midoriya saved her? Is this a plot mistake or is there another explanation?
She was in shock from the explosion. as we see when she was stuck under the debris, she is struggling to get up. Also, Midoria acted on an impulse and without thinking and jumped in to save her so even if she was able to get out of the danger, she simply did not have the time to react before Midoria. The scene is not showing her weakness, it is showing that the test is not as easy as we think and anything might happen. in addition, we see that Midoria acting without hesitation to save a person in need is part of his personality and not just a one-time thing and not just for his friends.