☰ Contents · Natural science

Physical phenomena; motion and force

Lessons 51–52 · 2 lessons · Y.V. Malikova, S.V. Kosyanenko. Natural Science Grade 4, Part 1. Novda Edutainment, Tashkent, 2023; S.V. Kosyanenko, Y.V. Malikova, O.E. Tigay. Natural Science Grade 4, Part 2. Novda Edutainment, Tashkent, 2023
52

Motion and force

Textbook: Part 2, pp. 82–85
GoalKnow motion and rest, speed, what force is, and that force can start, stop or change the shape of a body.
New words
force · kuchspeed · tezlikmotion · harakatrest · tinch holat
Explanation

A body is moving if over time it changes its place compared with other bodies. A person sitting by the road is at rest next to a building, yet moves with the Earth around the Sun. Speed is the distance a body covers in one unit of time, such as an hour. For example, a bicycle may travel 15 km an hour and a car 60 km an hour. A push or pull that starts a body moving, stops it, changes its direction or changes its shape is called force. Kick a ball and it starts moving; catch it and it stops; press plasticine and its shape changes. Force comes from bodies acting on each other and is measured in newtons. Force is not energy: force is an action, energy is the ability to do work.

Worked examples
Distance: at 60 km/h in 2 hours is 120 km.
Class activity

Push the same toy car on a table with different force and measure how far it goes. Does a harder push send it further?

Practice
1
How can a force act on a body?
2
A bicycle at 15 km/h: how far in 2 hours?
3
In what unit is force measured?