While driving on the interstate, the car in front of my stepped on their brakes hard and immediately let off. I was several car lengths behind the car, but my emergency braking activated. The brake pedal went out of reach and I tried to step on the gas but the car would not accelerate. Two cars passed me on both sides, but luckily there was no one behind me or they would have hit me. The car went down to approximately 20 mph before I could again accelerate. The car in front of me was nearly 1/4-mile away at that point