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Bikes and cars are both machines used to move people

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Two machines we see and use in everyday life are bikes and cars. Both of these machines are called vehicles because they are used to help move people around. Both bikes and cars use many different machine parts in order to turn their wheels to make the machines, and the people using them, move. Below we will talk about the different parts of these machines and the forces that act on them.


Bike and cars get their power in different ways

Bikecarpower Bikes use people power, which comes from the food people eat. Cars are powered by gasoline or electricity.
Bikes are a more basic machine than cars because they use human power to create motion. The person riding the bike uses the chemical energy from in their body to move their legs. This chemical energy is created as a result of the food you eat. The leg movement rotates the pedals, which are connected to a set of gears that turn a chain. This chain is connected to the wheels, so that when the chain turns, the wheels turn.

Car engines are powered by burning gasoline. When a car engine burns gas, it releases a huge amount of energy inside of pistons, which are cylinders with parts inside that move up and down. The energy released is used to create motion in the car, by guiding the energy to the axles, the part of the car that spins the wheels. There are four steps in the process to turn the fuel into movement which can best be remembered by these four words: Suck, Squeeze, Bang, and Blow. To learn more details about this process, check out the Motors and Engines section.


Many different machine parts are combined to make up bikes and cars

Bikecarsimplemachines Bikes and cars include parts like wheels and axles, gears, frames, engines, and many more.
Both bikes and cars use parts to help with the steering of the vehicle, turning of the wheels, creating a forward force, and transferring power from the power source to the wheels. Bikes and cars do some of these things differently and some of them the same.

Bikes steer by having the person riding the bike turn the handlebars. These handlebars are directly connected to the front wheel of the bike. Therefore, the person riding the bike must move their arms the exact distance that they would like to turn the bike tire.

Cars steer by using a steering wheel on the inside of the car. Then power steering is used to maximize the force applied by the driver to the wheel. Power steering makes it easier for the driver to turn the wheel of the car. This way the driver doesn’t have to overcome the full force of the car to be able to turn. The steering wheel is connected to a system that translates the turning motion of the steering wheel to the motion of the tires.

Both bikes and cars use tires on their wheels to create traction with the ground. By creating increased traction, they create a greater forward force. These tires are mounted on a simple machine, a wheel and axle, to allow for rotation and maximize the mechanical advantage gained from the system. Read more about wheel and axles systems in the Simple Machines section.

Cars also have many other parts incorporated for things like safety, comfort, and ensuring that other parts of the car work correctly. These do not have an impact on the forward motion of the car but are important for making the car work. Some of the safety parts include seat belts, mirrors, and air bags. Some of the parts included for comfort are air conditioning, cushioned seats, and a radio. Some of the parts that monitor other parts of the car include a speedometer, which tracks how fast the car is moving, and the fuel gauge, which tracks how much gasoline is left in the car. You could still have a working car without all of these things, but it would not be as safe or as enjoyable to ride in! Many engineers work on improving these parts of the car as well as the engine and tires.


Friction is one of the main forces acting on bikes and cars

Bikefriction Friction with the ground is what allows the force applied to the tires of bikes and cars to move the vehicles.
Friction is what allows bikes and cars to create the traction they need with the ground in order to make a forward force. The greater the friction force on the tires, the less energy that is wasted by the tire spinning without creating forward motion. Lack of friction becomes a problem for people riding and driving on icy or snowy surfaces. This is because they are slicker and make it harder to create the needed friction.

However, friction isn’t always helpful for bikes and cars. Drag is a type of friction that is caused by air rubbing up against the surface of the vehicle. Drag is a common problem among fast forms of transportation like cars, trains, planes, and rockets. The higher the amount of drag, the more energy has to be used to make the vehicle move. Therefore, engineers are working to minimize drag forces on cars by creating more sleeker and aerodynamic shapes. Engineers perform tests to see how to make air flow around the vehicle better. These tests help them fine-tune the shape of the vehicle to reduce drag. You can read more about drag in the Friction section.


Bikes and cars both transfer energy between many parts to allow for forward motion

Bikes use the power of a human to power the bike forward. A bike does this by transferring the energy that was applied by a person to the pedals to move a chain on the bike. This chain is connected to the bike wheels that then turn, creating traction with the ground and moving the bike forward. Handlebars are used to turn the bike.

Cars use the power created by a heat engine to move pistons. These pistons then turn a drive shaft that transfers this power to the wheels of the car. The car is designed in an aerodynamic way so that drag is minimized.


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