Quantity explained to kids

A quantity is a value that expresses a magnitude, amount, or size. There are two types of quantities: scalar and vector. Scalar quantities have magnitude only, while vector quantities have both magnitude and direction. Some examples of scalar quantities are mass, speed, temperature, and time. These can be measured with units such as kilograms (kg), meters per second (m/s), degrees Celsius (°C), and seconds (s). Vector quantities have both magnitude and direction. Some examples are velocity, acceleration, and force. These can be measured with units such as meters per second (m/s), meters per second squared (m/s2), and newtons (N). In order to calculate with quantities, we need to be aware of the units that they are measured in. This is because the units cancel out when two quantities of the same type are multiplied or divided. For example, if we want to know how long it will take an object to travel a certain distance at a certain speed, we can use the equation: distance = speed × time If the distance is in kilometers (km) and the speed is in meters per second (m/s), then the units of time will be in seconds (s). This is because the units of km/m cancel out, leaving us with s. Similarly, if we want to know an object's velocity, we can use the equation: velocity = distance ÷ time If the distance is in kilometers (km) and the time is in hours (hr), then the units of velocity will be in kilometers per hour (km/hr). This is because the units of km/hr cancel out, leaving us with km/hr. It's important to be aware of units when working with quantities because they tell us the meaning of the answer. For example, if we want to know how long it will take an object to travel a certain distance at a certain speed, and the answer we get is in seconds, then we know that this is the time it will take the object to travel the distance, not the distance the object will travel in a certain amount of time.