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SVA03
ALTERNATIVE ASSESSMENT
TASK
IEB
MASTER SCIENCE
wave."
and turned around to paddle away from it with all I have to enable me to get into the
Aaron recalled his record 19,2 m wave: "I saw a huge wave approaching on the horizon
for 12 seconds until he reached a speed of 4 ms-', when the wave caught up with him.
It was determined that he started paddling (away from the wave) from rest, and paddled
The combined mass of Aaron and his surfboard is 85 kg. The wave was moving at a
constant speed of 45 km-h-' towards Aaron
1.1.
What is the net force acting on the wave? Explain your answer.
1.2
What was the speed of the wave, in meters per second?
1.3
How far did the wave travel during the 12 seconds that Aaron was paddling away
from it?
(2)
"Heriotary
(1)
(3)
(5)
1.4
Determine the magnitude of the net force on Aaron and his surfboard during the
12 s period during which he paddled from rest to 4 m.s-'.
1.5
What was the distance between Aaron and the wave when he started paddling
(4
away from it?
1.6
Draw a rough position vs time graph for the motion of Aaron as well as for the
wave on the same set of axes, from the moment he started paddling until the wave
caught up with him. Indicate all relevant points on the axes.
(6)
mi
IEB
MASTER SCIENCE
The take-off
ALTERNATIVE ASSESSMENT
TASK
SBA
SVA03
The most crucial part of catching a wave is the "take-off" where the surfer stands up on
the board (after matching the speed of the wave), and then surfs down from the top
(crest) of the wave to the bottom (trough). Big oceanic waves move much faster than
wave surfers use specifically designed surfboards (called "guns") which help them to
smaller waves (due to many reasons beyond the scope of our curriculum), therefore big
speed, to gain enough speed to match up to that of the wave. A "gun" surfboard is the
use more of the mechanical energy of the wave, in combination with their own paddling
same width, but longer and thicker than a normal surfboard (called a "shortboard");
Keeping your balance while standing an is tricky because the forces acting on the board
need to be balanced.
Fig.2: Twiggy Baker
on a critical moment
during the take-off.
Image: http://stabmag.com/news/heres-why-twiggy-baker-was-banned-from-the-
mavericks-event/
Assume that the 19,2 m wave kept on moving at a constant speed of 45 km.h when
Aaron was riding it.
What was Aaron's speed, relative to the wave, at the top of the wave as he started
the "take-off"'?
2.1
(1)
What was Aaron's speed, relative to the earth, at the top of the wave as he started
the "take-off"'?
2.2
(1)
(2)
2.3
What is "mechanical energy"?
What was Aaron's mechanical energy at the top of the wave? (Aaron and his
board are a single system)
2.4
(4)
Calculate Aaron's speed (in km · h-'), relative to the earth, at the bottom of the
wave if all effects of friction are ignored.
2.5
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TASK
on his board moving along
le in surfing, and cannot be ignor"
:
ALTERNATIVE ASSESSMI
Schoolwer
IEB
ALTERNATIVE ASSESSMENT
SBA
MASTER SCIENCE
TASK
SVA03
Surfboard design
The following pictures of surfboards show the shapes of 3 types of surfboards compared to
each other by design (e.g. length, width, surface area, volume, mass, etc.).
Allinear su
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200
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A) Shortboard (3 kg)
Surf Scienco
B) "Gun" (7 kg)
C) Longboard (12 kg)
Images from: http://www.surfscience.com/
All 3 of the surfboards above are made from the same materials and their masses are
representative of their volumes. A longboard is the thickest followed by a "gun" and
then a shortboard.
Which of surfboards A, B or C will
3.1.1 have the most manoeuvrability?
3.1.2 have the most inertia when moving on a wave?
3.1.3 be the best for a beginner (struggling with balance) to learn to surf with?
3.1.4 need the smallest force to paddle from rest?
3.1.5 exert the greatest lift (upwards force) on a surfer?
3.1
(5)
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MASTER SCIENCE
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ALTERNATIVE ASSESSMENT
D
dams plays a very important role in surfing, and cannot be ignored.
lowing diagram represents a surfer on his board moving along a wave.
2.6.1 normal force
2.6.2 frictional force
2.6.3 weight
beeswax.
Which letter (A -D) in the diagram represents the direction of the:
(3)
(4)
27 Surfers increase the friction on one surface of their boards by rubbing it with
2.7.1 Should the friction between the water and the board be high or low?
Explain your answer by referring to the appropriate Newton's Law.
2.7.2 Should the friction between the surfer's feet and the board be high or low?
Give a reason for your answer.
2.7.3 Refer to your answers in Q 2.7.1 and Q 2.7.2 to deduce whether surfers
wax the top surface or the bottom surface of their surfboards.
(5)
(2)
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SVA03
mi
ALTERNATIVE ASSESSMENT
MASTER SCIENCE TASK
(4)
2 It takes a lot of skill for a surfer to balance all the forces acting on a surfboard
while riding a wave A very important skill in surfing smaller to medium waves is
the ability to slow down or to speed up when riding the wave. Which surfboard
design (A Bor C) will test allow a surfer to quickly change velocity when riding
a wave? Explain your choice by naming and applying the relevant Newton's
Law(s) of motion
(4)
33 Give no reasons why a "pun" is used in big wave surfing, rather than a
longboard, and motivate each reason with an explanation using appropriate
Mechanics terminology
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