Understanding Force

Weeks Date Content Time (Period)

1 May 18- 22 Class Orientation 1 Lesson 1 Forces and Motion (Chapter 7) 1

2 May 25-29 Understanding Force 1 Resultant Force on the Same Plane (Net Force) 1

3 June 1-5 Resultant Force on the Same Plane (Net Force) 1 Resultant Force on Static Objects and Moving Objects with Constant Velocity

1

4 June 8-12 Resultant Force on Static Objects and Moving Objects with Constant Velocity

2

5 June 15-18 Long Quiz (5 Mark) 1 Lesson 2 Element and Mixtures (Chapter 5) (5.1) Elements 1

6 June 22-26 Elements (con…) 2 7 June 29-July 3 Compounds 2 8 July 6-10 Mixtures 1

Separation Techniques 1 9 July 13-17 Separation Techniques 1

Radioactive Elements 1 10 July 20-24 Midterm Exam 11 July 27-31 Lesson 3 Energy and Chemical Changes (Chapter 6)

(6.1) Physical and Chemical Change 1

Chemical Equation 1 12 August 3-7 Energy and Chemical Reactions 2 13 August 10-14 Factors Affecting the Rate of a Reaction 1

Chemical Reactions and Chemical Substances in Everyday Life 1

14 August 17-21 Chemical Reactions and Chemical Substances in Everyday Life

2

15 August 24-28 Lesson 4 The Earth (Chapter 6) Layers of the Earth

1

Rocks 1 16 August 31-Sep. 4 Minerals, Fossil Fuels, Natural Water 1

Lesson 5 Soil (Chapter 9) Soil

1

17 September 7-11 Soil Formation 1 Soil Uses and Soil Improvement 1

18 September 14-18 Final Test

W= f x d Forces Distance

Unbalanced Spring scale Acceleration

Newtons Balanced Work

Mass

Can be measured with a

In units of

Can be

Can be calculated as

Can produce

If acted over a

As calculated by

No change in motion

change in motion

FORCE

Spring Scale

Newton

Balanced Unbalanced

mass Acceleration

Work

Distance

W= F x d

ACTIVITY 1Force and Motion

Vocabulary 1

Define the following:1. Force2. Net force3. Velocity4. Newton (N) (not the scientist)5. Gravitational Force6. Magnetic force7. Electrostatic force8. Frictional force

ISAAC NEWTON

Born in Woolsthorpe, England in 1642.Developed a powerful Mathematical tool called CalculusHe proposed the Three Laws of Motion which is taught to all physics students and schools.Discover the universal law of gravitation.Suggested that the force of gravity that pulls an apple to the ground is the same as which causes the Moon to revolve around the Earth, and the Earth to revolved around the Sun

Questions to Understand Force

1. What is force?

2. What are the types of force?

3. How to measure force?

We used force to hit a ball. What is force?

What is a force?

• A push or a pull• May be unbalanced or balanced

Unbalanced

Balanced and Unbalanced Forces

• Balanced forces exerted on an object always produce zero resultant

• Unbalanced forces exerted on an object always produced a resultant

Unbalanced

Although we cannot see force, the effects of force can be seen or felt.

(a) A stationary object to move(b) A moving object to change its speed(c) A moving object to change its direction of

motion(d) A moving object to stop moving(e) An object to change its shape

The action of force can cause:

A moving object to change its speed

What are the types of force?1. Gravitational force

2. Magnetic force

3. Electrostatic force

4. Friction (Frictional Force)

• Gravitational force by definition, this is the weight of the object. “that’s why things fall to the ground”

• Magnetic force is the attraction or repulsion that arises between electrically charged particles because of their motion

• Electrostatic force deals with phenomena due to attractions or repulsions of electric charges but not dependent upon their motion

• Frictional force is the force exerted by a surface as an object moves across it or makes an effort to move across it.

Vocabulary Check!

The strength of force is measured in Newton (N). This is named after Sir Isaac Newton, a great English Scientist and Mathematician. A spring balance is one common instrument used to measure force.

How to measure force?

Resultant Force on the Same Plane (Net Force)

Lets define resultant force… • It is when more than one force are acting on an object at a time.• It is also called a combined forceExample:• Two people pushing a car

- each person is applying a force on the car and the forces combine to move the car forwardHowever, as force is a vector quantity, the direction of each force matter.

- It depends on the magnitude and direction of each force.

… It depends upon the magnitude and direction

Example: (Parallel Forces)(A.)

Resultant force = -10+(-5) = - 15 NDirection of resultant force is to the left

(B.)

Resultant force = 10 + (-5)= 5 NDirection of resultant force is to the right

5N10N 15N

Resultant Force

5N 10N 5N

(C)

What is the resultant force of the object?Resultant Force = 6 + 4 + (-5) + (-5) = 0 NThe resultant force is 0 N. Therefore there is no resultant force acting on the object.

Remember:If the sum is positive, then the direction is to the right.If the sum is negative, then the direction is to the left.If the sum is zero, then there is no resultant force on the object

5N5N

4N6N

Bring the following next meeting:

1. Protractor2. Ruler3. Calculator4. Pencil

Non- parallel forces

• To find the resultant of two non-parallel forces, it is with two ways:– To draw scaled diagrams– Use the parallelogram of forces methodThe parallelogram is a method of finding the

resultant where the vectors are not in line, like in the situations figure shown in page 154.

Let’s learn the example given from your book….

Another example: Find the resultant force of two vectors 30 N and 40 N, acting on an object . The angle between the two forces is 680 . Scale: 1cm=10 N

Show your solution and diagram.