Why does the rpms on my car goes to 6 when I'm doing 40 mph? When I hit a curb

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I hit a curb on the passenger side front after that I smelled rubber burning and my Car started sounding funny and drove different I was doing 40 mph and my RPGs was between 6 and 7. On the manifold on right side I see it is wet and left side is dry. I checked the oil it was ok, the car didn't over heat. The car was parked for two hours after I hit the curb. What could it be?