FORCES

FORCES AND MOTION

Prepared by: Teacher Mae P. Tagarao

​SCIENCE 8 QUARTER 1 WEEK 1

​WHAT IS A FORCE?

Force can be operationally defined based on observed effects. This means that a force can be described in terms of what it does. However, forces do not always cause motion. It does not necessarily follow that forces acting on an object will always cause it to move.​

​The following figures are examples where forces have tendency of changing the motion of an object or not.

Multiple Choice

Look at the image on the left. In letter A, is the ball at rest?

• YES

• NO

Multiple Choice

How can you make the ball move in letter A?

• A. The ball has to be pushed or pulled.

• B. The ball has to be pulled only.

Multiple Choice

In letter B, what happens to the ball

when you push it with enough force?

• A. The ball moves in

  the same direction

  as the force.

• B. The ball does not

  move.

Multiple Choice

In letter C, while it is

moving, how can you

make the ball stop?

• A. Exert a force

  opposite the motion

  of the ball.

• B. The ball has to be

  pushed in the

  same direction of

  its motion.

Multiple Choice

In letter D, how can

we make the ball

change its direction?

• A. The ball has to be

  pushed sideways.

• B. The ball has to be

  pushed in the

  same direction of

  its motion.

Open Ended

What can forces do?

​Force is a push or a pull. It can make objects move, stop, or change their direction of motion.

​

An object maybe acted upon by several forces. For example, an object may be pushed and pulled in different directions at the same time. To identify which of these forces would be able to cause change in the motion of the object, it is important to identify all the forces acting on it.

​

​

​Forces are described in terms of (1) magnitude. Magnitude refers to the size or strength of the force which is commonly expressed in Newton (N); (2) direction of the force, (3) point of application and (4) line of action.

​

​

​TYPES OF FORCES

​1. CONTACT FORCES - forces where objects touch or contact with each other.

​

​2. NON-CONTACT FORCES - forces where objects do not touch or contact with each other. These forces act over a zone or area called field.

​EXAMPLES OF CONTACT FORCES

​EXAMPLES OF CONTACT FORCES

​EXAMPLES OF CONTACT FORCES

​EXAMPLES OF CONTACT FORCES

​EXAMPLES OF NON-CONTACT FORCES

​EXAMPLES OF NON-CONTACT FORCES

Fill in the Blanks

WHAT ARE THE TWO TYPES OF FORCES?

BALANCED AND UNBALANCED FORCES

​If two forces acting on an object are equal in magnitude but opposite in direction, they are considered as balanced forces. These forces must lie along the same line. If the forces are balanced, the objects either stay at rest or continue to move at constant velocity.

​If the sum of the forces equate to zero, they are considered balanced. The algebraic signs + and - are used to indicate the direction of forces. Unlike signs are used for forces acting in opposite direction.

BALANCED AND UNBALANCED FORCES

​Forces that cause a change in the motion of an object are unbalanced forces. Unbalanced forces are not equal and in opposite direction.

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