Have you ever tried rock climbing?

Rock climbing is a cool but physically demanding sport that involves climbing up big rocks using ropes, harnesses, and special gear.

You can imagine rock-climbers as Spider-Man, but without the Spidey-sense and cool suit.

🧗🏼‍♀️ Fun Fact: In fact, for the world to witness how physically demanding rock climbing is, rock climbing was introduced as an official sport in the latest 2020 Olympics in Tokyo, Japan.

As I watched the rock-climbing Olympians on TV in awe, I noticed that they will always apply some white powder on their hands before they scale the walls.

That made me wonder: What is that white powder and why do they apply it on their hands before they scale the wall?

Before we explain the use of the white powder, let’s have a look at this question from the 2018 Singapore Chinese Girls’ School (SCGS) P6 SA2 Examination Paper and discuss the concepts tested.

## Let’s Take A Look At This Question

Source: Singapore Chinese Girls’ School (SCGS) – 2018 P6 SA2 Examination Paper [Q35]

## Thought Process

To analyse this question, let’s first highlight the key information to look out for in the question.

From the question, we learn that the white powder rock climbers apply is chalk! We also learn two other pieces of key information, which I’ve highlighted in the question above.

🪨 Key Information 1: The rock-climbing chalk absorbs moisture.

🪨 Key Information 2: The rock-climbing chalk prevents Belle from falling during her climb.

To answer the question above, similar to other Forces questions, let us first identify all the forces present when Belle is rock climbing. Following this, we will then discuss which force causes Belle to fall during her climb and which force prevents Belle from falling during her climb!

### Analysing Forces Involved During Rock Climbing

When Belle is climbing up the wall, there is a force acting on her that is pulling her downwards towards the Earth’s surface due to her mass.

What is this force?

Answer: This force is the gravitational force acting on Belle.

Since gravitational force pulls Belle downwards towards the ground, does this force cause Belle to fall or prevent her from falling during her climb? The gravitational force pulling Belle downwards should cause Belle to fall during her climb.

In that case, how is Belle still able to stay on the wall? There must be another upwards force that allows Belle’s hands to grip the rock-climbing holds and prevent her from slipping and falling during her climb.

What is this force?

Answer: This force is the frictional force between Belle’s hands/shoes and the rock-climbing holds.

Since there is already frictional force between Belle’s hands and the rock-climbing holds for Belle to grip onto the rock-climbing holds, why does Belle still need to apply chalk on her hands?

Combining what we have learnt above:

Frictional force between Belle’s hands and the rock-climbing holds is the force that prevents her from falling during her climb.”

with the key information 1 and 2 below:

🪨 Key Information 1: The rock-climbing chalk absorbs moisture.

🪨 Key Information 2: The rock-climbing chalk prevents Belle from falling during her climb.

We can understand that:

On the other hand, this also implies that:

What is this moisture that can be found on Belle’s hands? You guessed it! It is her sweat.

Since Belle is participating in a very vigorous exercise, her body must be producing sweat, which could also be produced in the palms of her hand.

How does the moisture (sweat) on Belle’s palms result in less friction between her hands and the rock-climbing holds, which might cause her to fall more easily during her climb?

Let me provide you with an example to explain the above.

### Example: Opening A Jar Lid With Wet Hands

Have you ever tried opening a tightly closed lid of a jar with wet hands? If you have tried, do you find it easy to open the jar? No!

Why not? It is because the wet hands are “slippery” and are unable to grip the lid firmly.

And why are the wet hands “slippery’? That is because your wet hands contain water, which acts as a lubricant.

🫙 A lubricant is a smooth liquid.

When applied on two surfaces, it helps to reduce friction between the two surfaces when they rub against each other.

As such, the water on your wet hands acts as a lubricant and reduces friction between the hands and the lid, causing your hands to have a weaker grip on the lid. Thus, it is more difficult to remove the lid from the jar.

How does the above example explain why the moisture on Belle’s palms might cause her to fall more easily during her climb?

As a result, the moisture (sweat) on Belle’s palms might cause her to fall more easily during her climb.

Now that we understand how the moisture (sweat) on Belle’s palms might cause her to fall more easily during her climb, let’s summarise how the moisture-absorbing rock-climbing chalk can prevent Belle from falling easily during her climb.

“Since the chalk absorbs moisture (sweat) from Belle’s hands, would there be more or less moisture (sweat) on her hands?”

Answer: There would be less moisture (sweat)!

“With less sweat to act as a lubricant, would there be more or less friction between her hands and the rock-climbing holds?”

Answer: There would be more friction between her hands and the rock-climbing holds, causing her to have a stronger grip on the holds and preventing her from falling easily during her climb.

Belle’s hands produce sweat, which acts as a lubricant and reduces friction between her hands and the rock-climbing holds.

The chalk on her hands then absorbs the sweat, keeping her hand dry. This increases friction between the rock-climbing holds and her hands, gives her a better grip and prevents her from falling easily during her climb.

## Moving On To Another Question

Now, let’s look at another use of powder in this question from the 2017 Raffles Girls’ Primary School (RGPS) P6 SA1 Examination Paper.

Source: Raffles Girls’ Primary School (RGPS) – 2017 P6 SA1 Examination Paper [Q24]

In this question, it involves a game of carrom, a tabletop game of Indian origin where players use their fingers to flick coin-like discs, attempting to knock them to the little pockets at the corners of the board.

The question asks what the players should do before the game so that the carrom coins will move a longer distance on the board.

### Thought Process

The first thing we should consider is,

“Which force(s) affect(s) the distance travelled by the carrom coins on the board?”

Answer: Other than the amount of push force applied to flick the carrom coins, the distance travelled by the carrom coins is affected by the amount of friction between the carrom coins and the board.

🪙 The greater the amount of friction between the carrom coins and the board, the shorter the distance travelled by the carrom coins.

“As such, if the players want the carrom coins to move a longer distance on the board, should they increase or decrease the amount of friction between the carrom coins and the board?”

Answer: They should decrease the amount of friction between the carrom coins and the board.

Let’s look at the options given.

#### Option (1): Spread Powder On Carrom Board Surface

Now, in the earlier question, when chalk (powder) was applied to the rock-climber’s hands, the chalk (powder) helped to increase friction between the hands and the rock-climbing holds.

However, can powder also help to reduce friction when spread on a surface? Let’s find out.

When we look at a solid surface on a microscopic level, we can see that the surface is not entirely smooth. There are grooves and gaps on the surface as seen in the image below. When two solid surfaces rub against each other, it results in friction between the two surfaces due to these grooves and gaps.

What happens when powder is applied on a solid surface? The fine particles of the powder will fill up these gaps, creating a smoother surface.

“With a smoother surface, will there be more or less friction between the carrom coin and the board?”

Answer: There will be less friction between the coin and the board.

“With less friction between the coin and the board, will the coin move a longer or shorter distance?”

Answer: The coin will move a longer distance.

As such, option (1) is the correct answer.

#### Options (2), (3) and (4): Placing A Rubber Mat, Pasting Sandpaper & Scratching Surface Of Coin

For options (2), (3) and (4), these options would create a rougher surface and would cause an increase in friction between the coin and the board. Thus, the coin will move a shorter distance on the board, instead of a longer distance.

Thus, options (2), (3) and (4) are not the correct answer.

## Conclusion

As discussed above, when powder is applied in a rock-climbing event, it increases friction. However, when powder is applied on the surface of the carrom board, it actually reduces friction.

So how do we know when powder will cause an increase or decrease in the amount of friction? Here’s a table showing you the scenarios to look out for to determine whether powder increases or reduces friction.

I hope you have enjoyed reading this article and that this article has helped you gain a better understanding of the use of powder and how it affects the amount of friction between two surfaces.

Check out our other articles on the topic of Forces and continue to keep a lookout for our new articles! 🙂

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