4th Class Science Force, Work and Energy Measurement

     Measurement

We need to measure different things in our daily life like length of objects, height, weight (fruits, vegetables, etc.) quantity of milk, water and so on.

         Measurement of Length

In early days, people used body parts to measure lengths.

Cubit                                         Hand span

The metre is what we normally use for measuring lengths. Smaller lengths an measured in centimetres. Metre is written as m and centimetre as cm.

Measurement of Mass

Mass tells us how heavy or light an object is. We use weighing scales to find the mass of an object.

Just as we use metre for measuring length, we use kilogram for measuring mass. Smaller weights are measured in grams. Kilogram is written as kg and gram is written as g.

         Measurement of Capacity

Capacity of a container is the amount of liquid it can hold. Litre is the commonly used unit for measuring capacity. Smaller units are measured in milliliters. Litre is written as I and millilitres as ml.

           Some Other Units of Measurement

In everyday life we also need to measure things that do not involve length, mass, and capacity. Time and temperature are two such examples. Time is measured in seconds. The measurement of hot or cold of an object is called temperature. Temperature can be measured with the help of a thermometer.

     Which of the following is a unit for measuring length?

(a) Metre

(b) Litres

(c) Millilitres

(d) Kilogram

(e) None of these

Answer: (A)

Explanation 

For measuring length we normally use metre.

      Which of the following tells us how heavy an object is?

(a) Mass

(b) Volume

(c) Length

(d) Temperature

(e) None of these

Answer: (a)

Explanation

Mass tells us how heavy or light an object is.

Mars has a lower gravity than Earth, therefore a person weighing 100 kg (220 pounds) on Earth would only weigh 38kg (84 pounds) on Mars.

Only one third of the energy in burning coal reaches the consumer as electricity.

If 10,000 schools turned off their lights for one minute it could save $81,885.

Force: It is pull or push acting on an object.

Friction: Frictional force opposes the motion of a moving object.

Work: Work is said to be done when force is applied to move an object.

Types of Energy: There are two types of energy depending on the object at rest or motion i.e. potential energy and kinetic energy

Source of energy: It is the system from which energy can be obtained.