Grade 4 Science - Pulleys and Gears (2024)

FAQs

What are pulleys and gears Grade 4? ›

Pulleys are used singly or in combination to move an object from one place to another. Gears can be used in combination to change speed and direction of movements. Students will design and build pulley systems and gear systems, and will explore the advantages of each kind of system.

Gears Are Machines

Because the teeth fit together, when you turn one gear, the other one turns too! Gears come in many different sizes, which help them do work. If you connect one big gear with a small one, you can turn the big gear slowly and it will make the little gear turn quickly.

Smaller gears driving larger gears result in increased rotational speed while reducing the force output. Pulleys: Fixed pulleys can provide speed advantage by changing the direction of motion, allowing for faster movement in a desired direction. However, speed advantage is achieved at the expense of force advantage.

Pulleys and gears can help us to do work. For example, a crane can help to lift heavy items on a construction site. They do the heavy lifting that humans cannot do. Pulleys can also make things a little more convenient for us by changing the direction of a force.

There are three main types of pulleys: fixed, movable, and compound.

A pulley is a mechanical device which contains a wheel and rope/belt/chain to lift the heavy objects. The wheel of the pulley is generally fixed to a hinge and rotates on an axle or shaft.

Like pulleys, gears can be used to transfer forces and motion from one object to another. Some gear systems can also be used to change the speed and direction of the motion. Gears have teeth on them that interlock with teeth from other gears.

There are many types of gears such as spur gears, helical gears, bevel gears, worm gears, gear rack, etc. These can be broadly classified by looking at the positions of axes such as parallel shafts, intersecting shafts and non-intersecting shafts.

Pulleys are simple machines that can change the direction of force, making it much simpler for us to move objects. They also increase mechanical advantage when we use multiple pulleys together. This process decreases the amount of force required to lift something up.

The driven pulley is adjustable and the drive pulley is controlled by a mechanical action that will open or close the pulley based on rpm requirement. As the driven pulley is opened, the driven pulley will decrease in speed and the opposite, as the drive pulley is closed the driven pulley will increase in speed.

How do pulleys turn? ›

A pulley is a simple machine that consists of a rope and grooved wheel. The rope fits into the groove in the wheel, and pulling on the rope turns the wheel. Pulleys are generally used to lift objects, especially heavy objects. The object lifted by a pulley is called the load.

Point out that a pulley uses a “pulling” applied force, while a gear pushes another gear.

A gear is a wheel with teeth around its circumference. Gears are usually found in sets of two or more, used to transmit rotation from the axis of one gear to the axis of another. The teeth of a gear one one axis mesh with the teeth of a gear on another, thus creating a relationship between the rotation of the two axes.

Gears on a bicycle are an example of cone pulleys. The gears all rotate together. The chain that runs around the gears serves the same purpose as a rope on a pulley. Rather than moving a load, the teeth on the chain are pulled along, causing the bicycle and the rider to move.

Kids Definition

pulley. noun. pul·​ley ˈpu̇l-ē plural pulleys. : a small wheel with a grooved rim used with a rope or chain to change the direction of a pulling force and in combination to increase the force applied for lifting.

A pulley is a wheel that carries a flexible rope, cord, cable, chain, or belt on its rim. Pulleys are used singly or in combination to transmit energy and motion. Pulleys with grooved rims are called sheaves.

Gear and pulley drive systems are common methods of transmitting motion from a source to an end load.