My sedan has 80 HP engine. Will I have difficulty when travelling uphill?

no, that's why you have a transmission to give you multiple gears and a mechanical advantage. You might not have HP, but you have torque and thats what pulls hills. Big tractors have low hp (like 50 -90) and they pull heavy equipment and go up hills...

80HP would make a bicycle able to travel up a vertical hill given the traction. "Sedan" define which sedan of the 1000s that have been on sale over the years and that will give us the important power/weight ratio which will indicate whether you will encounter difficulties.

HP is the mechanical turning strength multiplied by the the rate at which the engine is spinning. So you could have a diesel with 150lbft of torque which will have no difficulties climbing a hill or small petrol engine. Again it will depend on the mass of the car that will determine whether the car is up to a hill.

Define "Uphill" cars are designed to be relatively versatile but may not be able to scale half mile 1 in 3 hills. All cars are designed with power/weight in mind and I would be surprised if you could find a road open to the public that a production car designed/built in the last 25 years that won't manage a hill in first gear.

Watch the video with tips:

http://www.youtube.com/watch?v=qd_YkqPK2jk