Grade 4 - Machines and their Mechanisms
List an example of something that uses a pulley mechanism
Crane, Well, Elevator etc.
List an example of protective equipment that humans use to keep us safe from the impact of forces.
Answers may vary. (eg. a helmet keeps our heads from being compressed)
List an example of something that uses a gear mechanism
Car, Clock, Bike etc.
Which of the following uses a pulley?
a) Bicycle
b) Clock
c) Water Well
d) Motorcycle
C
What is the difference between a simple machine and a complex machine?
A simple machine is a basic tool that helps apply force and do work. A complex machine is made up of two or more simple machines.
What is the difference between a static and dynamic load?
Dynamic loads are subject to change. Static loads stay the same.
Identify a positive and negative way that machines can impact the environment
Answers will vary.
Eg. A car produces gases that can affect the environment.
A train allows many people to travel to similar locations all at once, reducing greenhouse gases
Gears are used to change what three things?
a) Inputs, outputs and force
b)Pulleys, crowns and torque
c)Acceleration, braking and direction
d)Speed, direction and torque
D
Complete both blanks.
__________ motion is movement in a circular path.
__________ motion is movement that occurs in a straight line.
Rotary, linear
What is the difference between an internal and external force? Give an example for each.
Internal forces are forces that occur within a structure (eg. tension, compression, torsion and shear)
External forces are caused by external agents in a structure. An example could be wind or snow on a building.
Fill in all the blanks.
_________ bridges have an assembly of triangles for extra support.
________ bridges are held up by ropes attached to tall structures.
Truss, Suspension
8. A measure of the intensity of a force is known as _______________.
a) Magnitude
b) Weight
c) Speed
d) Direction
a) Magnitude
Complete all blanks.
_______ is a measure of rotational force.
_______ machines are made of two or more simple machines.
_______ are systems in a machine that can modify a motion
Torque, Complex, Mechanisms
Fill in all the blanks.
_______ bridges are the simplest type of bridge. They have a horizontal beam and a deck.
_________ bridges have a semicircle shape to provide support
Beam, Arch
___________ is the internal force when something is pushed inwards
Compression
What is an example of a non-contact force?
a) A baseball player hits a baseball with a bat
b) A construction worker uses a shovel to dig a hole
c) A skydiver parachutes out of a plane toward the ground
d) An author types a book on a laptop
C
Fill in the blanks about gears:
If the first gear is turning clockwise, the second gear will turn __________.
The fastest gear is always the _________ gear.
Counter-clockwise
Smaller
What is the direction and point of application of a force, like a box being pushed?
The direction is the course along which the force is moving (eg. the direction the box is being pushed)
The point of application is the exact location at which a force is applied to a body (eg. where the hand is on the box)
What is the input component of a bicycle (where the force starts)?
The pedals
Which is an example of an internal force on a bridge?
a) Pedestrians walking on the bridge
b) Tension on the bridge cables
c) Vehicles driving along the bridge
d) Snow collecting on the bridge
B