Transcript Spot the error - sacss-science

Spot the error
• Spot the error in the answers (in red)
• Tell your partner what is wrong with the
answer and what should be the correct way to
answer it.
• The correct answer is in blue.
• Describe the speed of the object below.
Speed
time
• The object is accelerating with constant speed.
• The speed is increasing.
• The object’s speed is increasing at constant rate.
• Explain how light pass through the optical fiber.
• The incident ray is larger than the critical angle
hence the ray is internally reflected.
• The angle of incidence is larger than the critical
angle hence the ray undergo total internal
reflection.
• Describe how sound from the loudspeaker
reaches all parts of the room.
• Sound particles vibrate and pass energy
from particle to particle and sound
travelled outwards as a longitudinal wave.
• The loudspeaker vibrates and cause the air
particles around it to vibrate and pass
energy from particle to particle and sound
travelled outwards as a longitudinal wave
/ in a series of compressions and
rarefaction.
• Describe the movement of particles in a solid.
• The particles are in an orderly arrangement and have strong
intermolecular force between them.
• The particles vibrate about their fixed position.
• Describe what happens to the particles in a solid when it is
heated.
• The particles when heated start to vibrate and pass their
energy to neighboring particles.
• The particles will vibrate more vigorously.
• When some wax is heated, it melts.
Describe the arrangement of the
molecules in the molten wax.
• liquid wax particles move around
one another freely.
• The liquid wax molecules are
irregular and they are very close
together.
• The molecules in the molten wax
are arranged in an irregular
manner.
• Describe how the water in
the kettle becomes hot.
• Hot air rises and cold air sinks so the water will be heated up
evenly by convection current.
• The heating coil heats up the water around the coil. The
water molecules expand and hence the hot water rises and
cold water sinks and convection current formed will heat up
the water evenly.
• The water near the heating coil is heated, expands, becomes
less dense and it rises. The cold water is pushed downwards
to be heated. Cycle continues and the convection current
produced will heat up the water evenly.
• The table on the right has a mass
of 400 kg. The contact area that
each leg has with the ground is
0.005 m2. Calculate the pressure
that each leg exerts on the floor.
• P = F/A = (400 x 10) / (4 x 0.005) = 200 kPa
• Pressure exerted by each leg
= 200 / 4
= 50 kPa
• P = F/A = (400 x 10) / (4 x 0.005) = 200 kPa
• Earth wire protects the user from
electric shock when it touches the
metal casing of an appliance that is
“live”. What may cause the metal
casing to become live?
• When the current leaks to the
casing.
• When the insulation of the live wire
is damaged and the bare live wires
touches the casing.
• What can be used to
protect against short
circuit?
• Fuse
• earth wire
• do not touch appliance or
switch when hands are
wet.
• Ensure that the insulation
for both live and nuetral
wire are not damaged.
• Describe how heat is transferred from the
flame to the water.
• Heat is transferred by radiation
and conduction.
• Heat is transferred by radiation and
convection from the flame to the bottom of
the pot. It is then transmitted by conduction
through the pot to the water.
5m
9.4m
8m
• The 50 g ball at the top of the
slope is pushed with a speed of
3 m/s downwards. What is its
kinetic energy when it reaches
the bottom of the slope.
• KE gained = PE lost
= mgh
= 50/1000 x 10 x 5
= 2.5 J
• KE gained = 2.5 J + initial KE
= 2.5 + ½ (0.05) (32)
= 2.73 J
• Define speed.
• Speed tells us how fast an object is moving.
• Speed is the rate of change of distance.
• An A# musical note played by an instrument has a
frequency of 554 Hz.
• Explain what is meant by a frequency of 554 Hz.
• It means the number of vibration made per second
by the instrument.
• It means the number of vibration made by the
instrument per second is 554.
• Explain why shiny containers are used to make
teapots.
• This is because shiny surfaces are poor radiator and
absorber of heat hence it will not lose heat easily
and can keep the tea hot for a longer period of time.
This is because shiny
surfaces are poor radiators
of heat so heat loss by
radiation is slower. Hence
tea can be kept hot for a
longer period of time.
• Explain why wool is a suitable material to be
used for gloves worn during winter.
• Wool is able to trap heat well and prevent
heat loss from the hands to the surrounding.
• Wool traps air and air is a good insulator of
heat hence heat loss to the surrounding by
conduction is reduced.