Frictional Force | Ob - Free Printable

Let’s solve this step by step.

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Part 1: Fill the spaces with words in the box

Words given:
two - Frictional - harder - against

First sentence:
“__________ force refers to the force generated by __________ surfaces that contacts and slide __________ each other.”

We know from science that frictional force is the force that happens when two surfaces rub against each other. So:

- First blank → “Frictional” (because it’s naming the type of force)
- Second blank → “two” (because friction needs two surfaces touching)
- Third blank → “against” (because surfaces slide *against* each other)

So first sentence becomes:
→ Frictional force refers to the force generated by two surfaces that contacts and slide against each other.

Second sentence:
“Friction makes it __________ for things to move.”

Friction opposes motion — so it makes moving things harder.

→ Final word: harder

✔ Part 1 Answers:
- Frictional
- two
- against
- harder

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Part 2: Circle the images that express Frictional force

Look at each image:

1. Boy pushing a cabinet – Shows “Force of Friction” labeled → ✔ YES, this shows friction.

2. Apple falling from tree – This is gravity, not friction → ✘ NO

3. Parachute with air resistance – Air resistance is a type of friction (fluid friction) → ✔ YES

4. Magnet attracting nails – Magnetic force, not friction → ✘ NO

5. Boy running – His feet push against ground; friction helps him run → ✔ YES (friction between shoes and ground)

6. Boy pulling a cart – Wheels or bottom of cart rubbing on ground → friction is involved → ✔ YES

Wait — let’s double-check #5 and #6.

In #5: The boy is running — friction is what lets his foot grip the ground to push forward. Without friction, he’d slip. So yes, friction is expressed here.

In #6: Pulling a cart — if it has wheels, there’s rolling friction. If dragging, sliding friction. Either way, friction is present. Also, the image may imply effort due to friction.

But note: In some curricula, they only count obvious labeled friction or direct surface rubbing. Let’s look again.

Actually, looking closely:

- Image 1: Explicitly labels “Force of Friction” → Definitely include.
- Image 3: Labels “Air resistance” — which is a form of friction → Include.
- Image 5: Boy running — no label, but friction is necessary for running → Often accepted as showing friction.
- Image 6: Boy pulling cart — likely involves friction between cart and ground → Also often accepted.

However, sometimes worksheets expect only clear cases. But since air resistance is included (which is less obvious), we should include all where friction plays a key role.

BUT — wait! Let’s check standard answers for such worksheets.

Typically, for “circle images that express frictional force”, they want:

- Direct contact + opposition to motion.

Image 1: Yes (labeled)
Image 3: Yes (air resistance = fluid friction)
Image 5: Yes (foot-ground friction enables running)
Image 6: Yes (cart-ground friction)

Image 2: Gravity → No
Image 4: Magnetism → No

So circle images: 1, 3, 5, 6

But let me verify with common teaching materials.

Actually, in many Level 3 science sheets, they might exclude #5 and #6 unless labeled, because friction isn’t visually highlighted.

Looking back at the images:

- Image 1: Has arrow labeled “Force of Friction” → Must include.
- Image 3: Has “Air resistance” → Which is friction → Include.
- Image 5: Just a boy running — no indication of friction → Maybe not?
- Image 6: Boy pulling cart — no label, but you can infer friction → Possibly include.

Hmm. To be safe, let’s think like a teacher.

The question says: “express Frictional force” — meaning the image should clearly show or represent friction.

Image 1: Clearly shows it → ✔
Image 3: Shows air resistance → which is friction → ✔
Image 5: Running — friction is implied but not shown → ✘ (unless curriculum teaches that running requires friction)
Image 6: Pulling cart — same thing → ✘

But wait — in Image 5, if he’s running, friction is what pushes him forward. It’s essential. Same with cart.

I recall that in many similar worksheets, they DO include running and pulling as examples of friction.

For example, when you walk or run, friction between shoe and ground prevents slipping — so it’s expressing friction.

Similarly, pulling a cart — friction opposes the motion, so you have to pull harder.

Given that, and since air resistance is included (which is less tangible), I think we should include 1, 3, 5, 6.

But let’s see the answer expected.

Alternatively, perhaps only 1 and 3 are intended, because they have labels.

No — the instruction doesn’t say “only labeled ones”. It says “express Frictional force”.

So any image where friction is visibly or conceptually expressed.

Final decision:

✔ Circle these images:
- Top left (boy pushing cabinet) — labeled friction
- Top right (parachute) — air resistance = friction
- Bottom middle (boy running) — friction allows running
- Bottom right (boy pulling cart) — friction opposes motion

So four images.

But let me count the boxes: there are six images total.

Images to circle: 1st, 3rd, 5th, 6th.

Yes.

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Now, compiling final answer.

Final Answer:

Part 1:
- Frictional
- two
- against
- harder

Part 2: Circle these images:
- The boy pushing the cabinet (top left)
- The parachute (top right)
- The boy running (bottom middle)
- The boy pulling the cart (bottom right)