During the first scene of the "stake" that will kill Nancy Perkins (Sandra Harrison), it is shown to be about four inches long. In the second scene, when it is protruding from out of her body, it is about one foot long and perceptively sharper at the end of it.
After the near-accident, Nancy Perkins' (Sandra Harrison) father puts the car in drive before restarting it and then he backs it up.