7th Grade: Forces & Interactions Unit Test ANSWERS
Name:_________________
Block:_______
Target 1: I can determine the factors that affect the strength of electric and
magnetic forces.
1.
(a)
Donna put a paper cup into a glass beaker.
She glued a magnet in the bottom of the paper cup.
She glued another magnet in the bottom of the beaker.
The magnets repelled.
paper cup
N
magnet
S
S
magnet
glass beaker
N
diagram A
not to scale
What two forces act on the paper cup and its contents to keep it in
this position?
1. GRAVITY
2. MAGNETISM/MAGNETIC FIELD
Adapted from Greenwich Literacy and Numeracy Centre
1
7th Grade: Forces & Interactions Unit Test ANSWERS
(b) Donna put 5 g of aluminum rivets into the paper cup.
It moved down a little as shown in diagram B.
N
aluminium
rivets
S
S
N
diagram B
not to scale
Donna plotted a graph to show how the mass of aluminum rivets
affected the distance the cup moved down.
6
5
4
distance paper
cup moved 3
down (mm)
2
1
0
0
(i)
10
20 30 40
mass (g)
50
60
Use the graph to find the mass that made the cup move down 4
mm.
12 g
(ii) Why did the graph stay flat with masses greater than 40 g?
THE IRON MAGNETS ARE TOUCHING, IT CAN’T BE MOVED
ANY FURTHER
Adapted from Greenwich Literacy and Numeracy Centre
2
7th Grade: Forces & Interactions Unit Test ANSWERS
(c) Debbie removed the 5 g of aluminum rivets and put 5 g of iron nails
into the cup.
N
S
iron
nails
S
N
diagram C
not to scale
The paper cup moved down more with 5 g of iron nails than with 5 g of
aluminum rivets as shown in diagram C.
Give the reason for this.
THE IRON NAILS ARE MAGNETIC – THEY ARE ATTRACTED TO
BOTH MAGNETS AND MAKES THE MAGNETIC PULL
STRONGER
Adapted from Greenwich Literacy and Numeracy Centre
3
7th Grade: Forces & Interactions Unit Test ANSWERS
2.
Alex makes an electromagnet.
She winds insulated wire around an iron nail.
She connects the wire to a power supply.
She uses the electromagnet to pick up some steel paper-clips.
a) The magnetic field around a coil of wire carrying current .......
A. Is a circular shape
B. Is a diamond shape
C. Is a square shape
D. Is the same shape as around a bar magnet
b) An electromagnet is used in a junkyard because .......
A. It can be turned on and off
B. It can’t be turned on and off
C. It is stronger than a permanent magnet
D. It is weaker than a permanent magnet
c)
Describe how she could use the paper-clips to measure the
strength of the electromagnet.
 SEE HOW MANY PAPER CLIPS IT WILL HOLD
 INCREASE THE NUMBER OF COILS AND SEE HOW MANY PAPER
CLIPS IT HOLDS
Adapted from Greenwich Literacy and Numeracy Centre
4
7th Grade: Forces & Interactions Unit Test ANSWERS
(d)
Alex wrote a report of her investigation.
What would an odd result suggest?
 CREATED A MAGNET THAT DIDN’T WORK
 MISCOUNTED THE NUMBER OF PAPERCLIPS
 MISCOUNTED THE NUMBER OF COILS
(e)
(i)
Which size paper-clips would Alex use to make her results more
accurate?
Tick the correct box. FIRST BOX
(ii)
Give a reason for your choice.
THE SMALLEST PAPER CLIPS WOULD GIVE THE MOST
ACCURATE RESULTS
Adapted from Greenwich Literacy and Numeracy Centre
5
7th Grade: Forces & Interactions Unit Test ANSWERS
Target 2: I can conduct and evaluate an investigation that proves that non-contact
force fields exist.
3. Jimmy plans an experiment to find the Earth’s magnetic field in his science
classroom. His results are not what he expected. Give 2 sources of magnetic
fields that may have affected his results.
1. ELECTRICAL CABLES
2.IRON/STEEL OBJECTS
4.Two objects have collected static electricity with the same charge. What would the
objects do when placed near each other?
A. repel
B. attract
C. nothing
D. stick together
5. Which form of electric discharge appears in nature?
A. rain
B. ocean currents
C. lightning
D. volcanoes
6. Why does static electricity move from you to a metal object after you have walked
over new carpet?
A. It is attracted to the metal.
B. It is attracted to you.
C. It is attracted to the carpet
D. It is made in your shoes.
7. How can you tell when static electricity has been discharged?
A. Heat is released that can be felt.
B. Light is released and you can feel a shock.
C. Static electricity gives off many different colors
D. The object begins to spin rapidly when it is shocked.
Adapted from Greenwich Literacy and Numeracy Centre
6
7th Grade: Forces & Interactions Unit Test ANSWERS
Target 3: I can argue that gravitation pull depends on the masses of two objects.
8. Describe what will happen to the space craft as it flies between these 2 planets
and why it happens.

IT WOULD BE PULLED TOWARDS THE LARGER PLANET

THE LARGER PLANET HAS MORE MASS

THE LARGER PLANET HAS A GREATER GRAVITATIONAL PULL
Adapted from Greenwich Literacy and Numeracy Centre
7