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Simple Machines in Cars and Trucks

Complex machines such as race cars and aircraft are built from very basic components, called simple machines. Simple machines transform applied force to provide a mechanical advantage, thereby increasing the work done. Simple machines are used through society, such as in cranes, door stops, fasteners, and ramps. Simple machines transform applied forces by increasing the distance over which the force is applied or by modifying the direction in which the force is applied. Levers, pulleys, and wedges increase the distance over which a force is applied, while wheels, screws, and inclined planes alter the direction in which a force is applied.


Levers are simple machines that multiply force across a fulcrum, or balance point. In some cases, the fulcrum is located between the load and the applied force, such as in a seesaw. In others, the load and the applied force are on the same side of the fulcrum and the load is located between the applied force and the fulcrum, such as in a wheelbarrow. And in some types of levers, the applied force is located between the load and the fulcrum, such as in a catapult.


A pulley is a rotating wheel with a cord around it that's used to lift a load. Pulleys provide a mechanical advantage by exchanging a linear force with a tangential force applied over the circumference of the pulley. The larger the diameter of the pulley, the less force is required to lift the load. Increasing the diameter of the pulley also decreases the rotational angle through which the pulley needs to be moved in order to raise the load.

Wheels and Axles

A wheel is a cylindrical object that turns about an axle. Rotating the wheel causes the axle to move in one direction. Accordingly, a wheel converts rotational force applied to the rim of the wheel into the linear motion of the axle. Increasing the size of the wheel decreases the amount of force needed to move the axle and decreases the rotational distance that the wheel must be moved in order to move the axle.

Inclined Planes

An inclined plane is a simple machine that extends linear work performed in one dimension along a second dimension, thereby reducing the amount of force need to move a load. For example, a ramp is an inclined plane that makes lifting an object onto a loading dock easier. Instead of needing to vertically lift the load, a person can push it along the ramp, providing a mechanical advantage proportional to the steepness of the ramp.


A screw is an inclined plane wrapped around a central cylinder. Screws provide a mechanical advantage by converting rotational motion into linear motion. Increasing the thread density of the screw decreases the amount of force required to move the screw but also increases the number of turns required to insert or remove the screw.


A wedge focuses force applied to a large area onto a smaller point, thereby multiplying the force directed to the surface. By focusing applied force, the wedge provides a mechanical advantage. For example, the head of a nail can be characterized as a wedge. Applying force to the large head of the nail drives the small tip of the nail into an object.

Simple Machines in Cars

Levers in Cars

Levers are used throughout cars and trucks in movable parts and joints. For example, hinges on car doors are examples of levers. By applying force to the outside of the door, the door rotates about the hinge in order to open or close.

Pulleys in Cars

Pulleys are essential components of cars and trucks, coupling the engine crankshaft to the drive belt. An engine contains pistons that move linearly up and down inside a combustion chamber. The pistons rotate a crankshaft pulley, which propels a drive belt. The drive belt circulates among other pulleys coupled to various engine components, activating water pumps, alternators, idlers, and air-conditioner compressors.

Wheels and Axles in Cars

The wheels and axles of a car or truck support the weight of the vehicle while enabling its motion. Rotating wheels exert a force on the road, propelling the car forward. The pistons moving linearly in the combustion chamber of the engine rotate the axle of the car, which in turn rotates the wheels. In large cars and trucks, multiple pairs of wheels are used to support the weight of the vehicle and increase the force exerted by the wheels on the road.

Screws in Cars

Screws are used as fasteners throughout a car or truck. Screws secure the body of the car to the frame. Without strong screws, the body of the car could detach, exposing vulnerable engine parts to dust and particulates from outside of the car. Screws are also used in car jacks, aiding in lifting and supporting the weight of a car when the wheels need to be worked on.

Inclined Planes in Cars

The sloped front of a car acts as an inclined plane, allowing air to flow over the car with minimal resistance. Race cars also have rear spoilers that can affect the amount of downward force exerted by the air on the car, helping to keep the car wheels in contact with the road at high speeds.

Wedges in Cars

Wedges are most often used in vehicle braking systems. Foot pedals also incorporate wedges; a large foot pedal transfers the force exerted by a driver's foot to a small shaft that is linked to the accelerator and brake mechanisms of a car.

Simple Machine Projects and Activities for All Ages

  • Tin Cans Pulley Experiment: Pulleys can be constructed out of many materials, such as tin cans and strings.

  • DIY Pulley Physics: Simple machines can be used to lift heavy weights, which you can see for yourself with this activity.

  • Lever Experiments for Kids: See how levers provide a mechanical advantage, making lifting objects easier.

  • How to Build a Catapult: The catapult was a transformational invention and an important development in mechanical engineering, and it was built on the simple lever.

  • Make a Paper Glider: Flying paper airplanes is a fun way to explore inclined planes and drag.

  • Wedges for Kids: Wedges are simple machines for transferring force between large and small surfaces and are fun for kids to play with.

  • Wedge Hands-On Activities: Kids can try different activities involving cutting to see how blades function as wedges.

  • Fine Motor Play With Screws and Anchors: Let kids experiment with screws and a screwdriver to see how a screw can be used to pull together and fasten two objects.


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