Grade 7 · Science · Unit 8 of 12
Structures & Forces
Shapes, balance and forces
What your child practises
Solid, frame and shell structures, centre of gravity and stability, symmetry, and the size, direction and point of application of forces, including tension, compression, torsion and shear.
Ontario Curriculum expectation: D2.1–D2.4 · classifying structures; centre of gravity; forces; symmetry
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
The weight of a bridge itself is called its…
- wind load
- live load
- dead load
- torsion load
Show answer
dead load
Hint: A dead load does not change. Live loads, like traffic, do change.
Question 2
A dancer on a tightrope holds a long pole. How does it help?
- It removes the force of gravity
- It makes the rope longer
- It adds heat to the dancer
- It helps keep the centre of gravity over the rope
Show answer
It helps keep the centre of gravity over the rope
Hint: The pole lets the performer shift weight and keep balance over the support.
Question 3
In '800 newtons downward at the top of a post', what does 'downward' tell you?
- the mass of the post
- the direction of the force
- the point of application
- the magnitude of the force
Show answer
the direction of the force
Hint: Direction is the way the force pushes or pulls.
Question 4
A truck driver loads heavy crates on the bottom and light ones on top. Why?
- It makes the truck lighter
- It lets the load roll more easily
- It keeps the centre of gravity low
- It makes the load look neat
Show answer
It keeps the centre of gravity low
Hint: Heavy things near the ground lower the centre of gravity.
Question 5
Solid, frame or shell structure? Sort each one.
Sort into: 🧱 solid · 🏗️ frame · 🥚 shell
- 🔺a stone pyramid
- 🧱a concrete gravity dam
- 🥫a tin can
- ⛑️a bicycle helmet
- 🚲a bicycle frame
- 📡a radio tower
Show answer
🧱 solid: a stone pyramid, a concrete gravity dam · 🏗️ frame: a bicycle frame, a radio tower · 🥚 shell: a tin can, a bicycle helmet
Hint: A solid structure is mostly filled with material. A frame structure is made of connected parts (beams and columns) with space between. A shell structure holds its shape with a thin outer layer.
Question 6
A beam bends under a load. The top edge is squeezed and the bottom edge is stretched. The top is under…
- no force
- compression
- torsion
- tension
Show answer
compression
Hint: The outside of a bend stretches (tension) and the inside is squeezed (compression).