Give reason
A bicycle moving fast on a levelled road moves up to a certain height on an
uphill road even without its being pedalled.
Answers
Answer:
The short answer: Gravity.. and, WHEELS!
Gravity is a constant force acting on everything surrounding a massive object. It keeps working whether the object is falling, or at rest. One other aspect of gravity is that 2 objects accelerate toward eachother faster and faster. How fast depends on how massive the two objects are. The more mass either object has, the faster they meet. In the case of cycling down a hill, the objects are the Earth, and you on a bicycle.
Imagine for a moment that you’re on the roof of a 67-story building. You cycle off the edge and what happens? Gravity pulls you and your bike at accelerating speed toward the Earth’s centre of mass. Not toward the ground, but toward an imaginary point inside the core of the Earth. You fall straight down and although you reach the ground, gravity does not stop acting on you. It’s only that the ground was in the way during your fall.
Imagine now that you and your bike are standing on the edge of a very steep hill (80 degrees, almost vertical). You cycle off it and what happens? The same force pulls you and your bike toward the Earth’s centre of mass, but this time there is some mass (a hill) under your wheels slowing you down slightly, and also changing your trajectory from straight down to forward. You’ll still be accelerating real f*cking fast. This holds true for any hill with any degree of incline. Exactly how fast you’ll be accelerating depends on the inclination of the hill (how steep it is).
Another factor is your wheels. Ah wheels, such a great invention. Wheels on a bicyle have an axis around which the ball bearings turn, making it possible to balance something on this axis (in this case a bicycle frame). The accelerated fall toward Earth’s centre of mass is picked up by the circular motion of your wheels and off you go. But as you roll, the rubber on these wheels makes contact with the hill, and so exerts friction onto the hill. The softer your rubber, the more friction it exerts onto the hill, slowing you down.
Harder tires results in less friction, higher speed. The surface area of your tires also influences friction. Thick tires have a greater surface area, creating more friction, resulting in a slower speed. Thin tires = less friction, higher speed. Sadly, thinner tires also mean less grip, possibly resulting in slipping.
And finally, the surface of the hill is equally important. A grassy and bumpy hill will be a slow descent compared to a hard and smooth hill