Forces
A student pushes a chair across the classroom. What is the name of the force applied by the student?
Push force
What non-contact force pulls objects toward Earth?
Gravity
When you lean on a wall, what type of force is the wall applying to you?
Normal contact force
Is a sound wave transverse or longitudinal?
Longitudinal
What unit do we use to measure sound intensity?
Decibels (dB)
A book is resting on a table.
Name two forces acting on the book.
Weight (Gravity) and Normal Force
A magnet attracts a paperclip without touching it.
What type of force is this?
Magnetic force
A skydiver feels a force pushing up while falling.
What contact force is this?
Air resistance
If a wave has a larger amplitude, what changes?
Energy increases (loudness if sound)
When light hits a mirror and bounces off, what is this called?
Reflection
A football slows down after being kicked.
Which force causes it to slow down?
Friction (and air resistance)
The Moon stays in orbit around Earth.
Which force keeps it in orbit?
Gravitational force
Why do shoes with rough soles prevent slipping?
They increase friction
A wave has frequency 5 Hz and wavelength 2 m.
What is the wave speed?
10 m/s
Why do we see a red apple as red?
It reflects red light and absorbs other colors
A box is pushed with 10 N to the right. Friction acts with 6 N to the left. What is the resultant force?
4N, to the right
Why does a charged balloon stick to a wall?
Electrostatic force
A spring stretches when you hang a mass on it.
What type of force is acting inside the spring?
Tension / elastic force
Why can light travel through space but sound cannot?
Light does not need a medium; sound does
When light enters glass from air and bends, what is this called?
Refraction
A car moves at constant speed on a straight road. Are the forces balanced or unbalanced? Explain.
Balanced as the resultant force is zero
Two astronauts are floating inside a spacecraft.
Why do they appear weightless even though gravity still acts on them?
They are in free fall orbiting Earth
Explain why friction can be useful and harmful in daily life. Give one example of each.
Useful for walking; harmful because it causes heat (burn your skin)
If frequency increases but wave speed stays the same, what happens to wavelength?
Wavelength decreases
A prism splits white light into colours.
Why does this happen?
Different colours travel at different speeds in glass (dispersion)