Grade 7 Physics Interactive Lab: Friction, Pressure, SI Units & Balanced Forces

Topic 7Kc

How Can We Control Friction?

Friction is the force between two touching objects. It can slow things down or make things stay still. Friction stops your clothes from sliding off chairs and keeps your feet firmly on the ground. Let's explore how friction is increased or decreased!

Friction Physics Simulator

Interactive Lab

Select a track surface, apply a starting push force, and observe stopping distance, heat generated, and friction forces!

Speed: 0.0 m/s

Friction Force: 0.0 N

Friction Temp: 25 °C

Select Track Surface:

Push Force (Newtons):

50N

Increasing Friction (Better Grip)

Materials like rubber produce high friction. Rubber tires on Formula One cars stop sliding on sharp turns, and rubber bath mats keep you from slipping!

Reducing Friction (Lubrication & Ski Wax)

Lubricants (oil, grease) and ski wax smooth contact surfaces. Oiling bicycle axles allows wheels to turn smoothly without excessive wear.

3 Major Effects of Friction

Wears Things Away: Bicycle brake pads and car tires wear thin.
Produces Heat: Car engines without oil overheat and stall.
Produces Noise: Rusty door hinges squeak loudly.

Science Fact: Formula 1 Racing Tires

F1 racing car tires are engineered to grip the track at extreme speeds. They wear out so fast that they only last an average of 120 km and cost over £1,000 (~$1,300) per tire!

Mini Game: Classifying Friction Applications

Drag & Drop / Tap Selection

Classify these everyday situations based on whether the goal is to Increase Friction or Reduce Friction!

Deep Treads on Bicycle Tires

Engine Oil in Cars

Rubber Bath Mat

Wax on Downhill Skis

Rock Climbing Shoe Soles

Lubricant Spray on Door Hinges

Goal: Increase Friction

Goal: Reduce Friction

Sci-Fi Story Challenge: "The Lubricating Mist"

Based on your textbook reflection question!

Imagine a mysterious lubricating mist moving towards a town. It coats everything in a frictionless liquid layer. What would happen to daily life in the town?

Write 3 main effects on the town (e.g., cars cannot brake, people slipping while walking):

0 / 150 words

Topic 7Kd

How Is Pressure Used in Sports & Daily Life?

Pressure is the amount of force pushing on a certain area. Key formula: Pressure (P) = Force (F) ÷ Area (A).

P

Pressure Formula

P = F / A

P = Pressure (Pa or N/cm²)
F = Force / Weight (Newtons - N)
A = Contact Area (m² or cm²)

Larger Surface Area

For the same force (F), a larger area (A) results in LOWER Pressure (P).

Example: Snowshoes spread weight to stop sinking into soft snow.

Smaller Surface Area

For the same force (F), a smaller area (A) results in HIGHER Pressure (P).

Example: Crampon spikes & sharp knife edges concentrate force.

Pressure Visualizer: Snowshoes vs Crampons

Textbook Case Study

Total Force (Weight): 800 N

Total Contact Area: 2400 cm²

Pressure (P = F/A): 0.33 N/cm²

Pressure Calculator Tool

Calculate pressure instantly by entering Force (F) and Area (A):

Force / Weight (F) in Newtons (N):

Contact Area (A):

Working Steps:

1. Formula: P = F / A

2. P = 800 N / 0.2 cm²

Result: P = 4000 N/cm²

Unit Note: 1 Pa = 1 N/m². If area is measured in cm², pressure is in N/cm² (1 N/cm² = 10,000 Pa).

Applications of Pressure in Everyday Life

1. Snowmobiles & Wide Tracks

Snowmobiles feature WIDE tracks and skis to increase surface area ($A$), lowering pressure so the heavy vehicle does not sink into soft snow.

2. Drawing Pin (Thumbtack)

Has a sharp point (tiny area → high pressure to pierce walls easily) and a large head (large area → low pressure so it doesn't hurt your thumb).

3. Sharp vs Blunt Knives

A sharp knife has an extremely thin cutting edge (tiny area $A$). Pushing with the same force concentrates pressure, making cutting effortless!

Topic 7Kd

What Are the Standard Units Used in Science?

Science requires a universal standard so scientists worldwide can collaborate without costly errors. Let's learn the International System of Units (SI) and its prefixes!

True Case Study: Mars Climate Orbiter Disaster (1999)

Why standardizing units is vital in science

$327 Million Loss

The Mars Climate Orbiter spacecraft disintegrated in Mars' atmosphere because two separate engineering teams used different sets of units!

❌ Engineering Team A: Used Imperial Units (Pound-force)

✔ Engineering Team B: Used SI Units (Newtons)

Without correct unit conversions, navigation data diverged, sending the probe too close to Mars where it was destroyed. That is why International System SI Units are mandatory for scientists globally!

Standard SI Units Table

Quantity	Unit Name	Symbol
Length	metre	m
Area	metre squared	m²
Mass	kilogram	kg
Time	second	s
Force	newton	N
Pressure	pascal	Pa (1 Pa = 1 N/m²)
Energy	joule	J
Speed	metres per second	m/s

SI Unit Prefixes Table

Prefixes are used when numbers are very large (e.g. food energy 10,000 kJ) or very small (e.g. leaf thickness in mm):

Prefix	Symbol	Multiplier / Meaning	Real Example
mega-	M	1,000,000	1 MJ = 1,000,000 J
kilo-	k	1,000	1 kg = 1,000 g
centi-	c	1 / 100 (0.01)	100 cm = 1 m
milli-	m	1 / 1,000 (0.001)	1,000 mg = 1 g
micro-	μ	1 / 1,000,000	1,000,000 µm = 1 m
nano-	n	1 / 1,000,000,000	DNA strand thickness

SI Unit Practice Challenge

Select the most appropriate SI unit and prefix for each measurement:

1. The thickness of a leaf:

2. Energy stored in your food:

3. Distance between London and Dubai:

Force Interactions

What Happens When Forces Are Balanced?

Forces can add together or oppose each other. When opposing forces are equal in size, they are balanced and speed remains unchanged. When one force is stronger, forces are unbalanced and speed changes!

Interactive Cyclist Force Simulator

STEADY SPEED

Adjust the forward pedaling force and backward friction force to see how forces affect speed!

Forward Force ($F_{fwd}$): 50 N

Friction/Drag ($F_{bwd}$): 50 N

Net Force: 0 N (Balanced)

Speed: 8.0 m/s

Forward Pedaling Force:

50 N

Backward Friction & Drag:

50 N

The 3 Motion States of Forces

1. Speeding Up (Unbalanced):
Forward Force > Backward Force. Object accelerates.

2. Steady Speed or Stationary (Balanced):
Forward Force = Backward Force. Speed remains constant!

3. Slowing Down (Unbalanced):
Forward Force < Backward Force. Object decelerates.

Why Don't You Fall Through a Chair?

When you sit on a chair or stand on a tightrope, you squash/stretch it slightly. Like a spring, it pushes back to balance your weight!

Test Weight on Spring / Tightrope:

500 N

Weight = 500 N ↓ | Upward Support Force = 500 N ↑ (Balanced)

Mini Game: Balanced vs Unbalanced Situations

Interactive Sorting

Decide whether forces are Balanced or Unbalanced for each scenario:

1. Rope Tug-of-War

The rope is not moving because pulling forces are equal and opposite.

2. Dog Sled Speeding Up

All dogs pull together with a force greater than snow friction.

3. Tightrope Walker Standing

The performer remains completely still on the stretched rope.

4. Bicycle Braking to Stop

Friction on brake blocks slows the bicycle down.

Lab Method Insight: Measuring Friction Force

To investigate friction between different surfaces, you must pull an object at a STEADY SPEED. Why? Because when speed is steady, forces are balanced—meaning your spring balance reading exactly equals the friction force!

Learning Assessment

Interactive Physics Quiz (Friction, Pressure, SI & Forces)

Test your understanding of topics 7Kc & 7Kd based on your textbook questions! Earn XP and unlock achievement badges!

Question 1 of 8 Quiz Score: 0

Grade 7 Interactive Physics Lab