The topic of Forces is usually taught in Primary 6 and I realised that many P6 students struggle to answer questions when two or more forces are involved.

Read Also

  1. Graph Question: Magnetic Force – Distance
  2. PSLE Science Misconception: Energy & Forces
  3. What Are Template Answers & Why Do They Matter?

As such, in today’s article, I will introduce the template answer required to tackle such questions.

 

What Do You Need To Know

Students are required to have an understanding on the four main types of forces:

  • Gravitational Force
  • Frictional Force/Friction
  • Magnetic Force and
  • Elastic Spring Force

Most students are competent in answering questions that involve only one type of force.

However, most examination questions do not simply test individual forces acting independently on the object. Questions typically test students on how two or more forces acting on the object interact. For these questions, students are usually able to identify which of the four types of forces are at work but encounter difficulties when they are structuring their answers.

 

Key Words/ Concepts

When there are 2 or more forces at work, there are a few steps students can follow:

Step 1: Identify what type of forces are at work.

Step 2: Identify the direction of the forces (Left? Right? Up? Down?)

Step 3: Group the forces together according to their direction.

Step 4: Identify which group of forces is stronger.

Step 5: Apply the template answer:

“The _____________ could not/ was not strong enough to overcome the _____________ (stronger opposing force).”

Note: It is important for students to use the word “overcome”.

That’s it!

With that, students will be able to nail similar questions using this step-by-step guide.

 

Let’s Take A Look At This Question Below

 

5 Easy Steps to Conquer Questions on Forces – 2015 MGS SA1 P6 Q33

Source: Methodist Girls’ School – 2015 P6 SA1 Science Examination Paper [Q33]

 

Here’s The Answer

 

Part (b)

Question: She observed that the shoe did not move when she first started pulling it. Explain this observation.

There are two forces acting on the shoe.

  • Pull force exerted by Flora
  • Frictional force

The two forces are acting in the opposite direction, with the greater force being the frictional force.

Hence the answer to part (b) would be:

The pull force was not strong enough to overcome the frictional force between the surface of the shoe and the ground.”

 

Part (c)

Question: Flora then moved the shoe up an inclined surface as shown below. She observed that more force was needed to start moving the shoe. Explain this observation.

There are three forces acting on the shoe.

  • Pull force exerted by Flora
  • Frictional force
  • Gravitational force (On an inclined surface, the normal contact force would not be able to balance the gravitational force acting on the shoe, unlike in part (b))

The pull force is acting in the opposite direction of the frictional force and the gravitational force, with the greater group of forces being the gravitational force and the frictional force.

Part (c) requires a slight tweak to the template answer as the question requires students to state the reason behind the larger force required. However, the word “overcome” is still required in the answer.

Hence, the answer to Part (c) will be:

“Some of the pull force was required to overcome the gravitational force acting on the shoe, besides the frictional force between the surface of the shoe and the ground.”

I hope that this article has taught you how to tackle questions on Forces using this simple 5-step guide!