SF.2.a.b Centre of gravity and Forces

An object's centre of gravity...(select all that apply)

• can be changed

• is always inside the object

• can be outside the object

• is never on the edge of an object

Tags

NGSS.MS-PS2-4

An object's centre of gravity can be precisely found by...

• using a ruler to measure the middle of the object

• finding the intersection of the two longest plumb lines

• finding the intersection of all plumb lines

• estimating the middle of the object

Answer explanation

If you support an object directly above the centre of gravity, the object is...

• hanging

• balancing (unstable equilibrium)

• in stable equilibrium

• in disequilibrium

Answer explanation

If you support an object directly below the centre of gravity, and the plumb line from the COG is within the base, the object is...

• hanging

• balancing (unstable equilibrium)

• in stable equilibrium

• in disequilibrium

Answer explanation

If a structure's COG plumb line is directly at the edge of the base of a structure, the structure is...

• hanging

• balancing (unstable equilibrium)

• in stable equilibrium

• in disequilibrium

Answer explanation

Tags

NGSS.MS-ETS1-1

Which vehicle will be more stable?

• Green car, because it has a lower centre of gravity

• Green car, because it has a wider track base

• Black car, because it has a higher centre of gravity

• Black car, because it has a wider track base

Tags

NGSS.MS-ETS1-1

NGSS.MS-PS2-2

NGSS.MS-ETS1-2

NGSS.MS-PS2-1

What are examples of forces on objects (select all that apply)

• Gravity (weight)

• Friction

• Applied force

• Thrust

• Loads

Tags

NGSS.MS-PS2-2

A force vector has two components:

• push, pull

• up, down

• speed, direction

• magnitude, direction

A block of cheese rests on a table. Which free-body diagram is correct?

• 1

• 2

• 3

• 4

Answer explanation

The cheese is resting, so the gravity (weight) of the cheese on the table must be balanced with an equal and opposite force of the table back up on the cheese (this is called the "normal force")

Tags

NGSS.MS-PS2-2

Given the free-body diagram of the car, we say this car is...

• Speeding up or slowing down

• At rest

• Moving at constant speed

• Either at rest or moving at constant speed. We can't tell.

Tags

NGSS.MS-PS2-2