Internal Forces
What is an internal force?
An internal force is a force that acts in the inside of a structure.
What is an external force?
An external force is a force that acts on the outside of a structure.
What are simple machines?
A mechanical device that changes the direction or magnitude of a force is known as simple machine. It makes our work easier.
What are compound machines?
Compound machines are machines that are made up of more than one simple machines. They are used to make work easier.
How many types of internal force are there?
There are 4 types of internal forces and their names are: Compression, Tension, Torsion ,Shear and Bending force.
How many loads do external force have and what are their names?
There are two types of load and their names are dead load and live load.
What are the different types of the simple machines? Name them.
There are 6 types of simple machines called: Lever, Wedge, Inclined plane, Pulley, Screw and Wheel & Axle.
Why compound machines can do more difficult jobs?
They can do more difficult jobs easily because their mechanical advantage is greater than simple machines.
What types of forces acts in Compression, Torsion, Shear, Tension and Bending ?
Compression is a force that squeezes something together.
Torsion is a twisting force.
Shear is the result of forces acting in opposite direction of each other.
Tension is a pulling force.
Bending is a pushing force.
Name the external forces acting on the buildings.
Wind, earthquakes, the weight of the people on the floors of the buildings, and the weight of the building itself are the external forces acting on the buildings.
Give two example of each simple machines.
Lever: A see-saw, hammer, shovel, wheelbarrow
Pulley: Pulley in Well wheel, crane ,elevator, flagpole pulley
Wedge: Knife, axe
Inclined Plane: Slide, skateboard ramp, slanted roof
Screw: Turbine, Nut and Bolt, Bottle Cap, Light Bulb
Wheel & Axle: Wheel Barrow, Steering Wheel of a Automobile, Doorknob,
Give two examples of compound machines and tell how many simple machines does it have.
Compound machines:
1.) Bicycle -It has a lever, a wheel & axle, a pulley and lots of screws.
2.) Scissors - It has 2 wedges and 2 levers with a fulcrum in the centre and the fulcrum in centre is also a screw so, a scissor uses 3 simple machines.
How do internal forces affect a structure?
The external forces such as wind, water and the vibration of the earth when an earthquake happens create internal forces within a structure. Internal forces such as shear, tension and compression can destroy the inner framework of a building or a bridge even though it is made of super strong steel and concrete.
What are dead and live loads? Give examples.
Dead load is a immovable load which means that it is permanently fixed. Live load is movable which means its not fixed permanently. Like a chair is on the ground is called dead load, but when I will sit on it, I will be a live load on the chair.
How can simple machines change the force?
Simple machines make work easier by multiplying, reducing or changing the direction of a force. Simple machines help us to change the direction of force and others to help increase the speed of work.
True/False
1) Compound machines make our work easier by changing the direction of force such as push or pull.
2) A machine such as a computer is a simple machine. 3) Wheel Barrow and pencil sharpener are compound machines.
4) Shovel is a compound machine made by 2 simple machines: Lever and Wedge.
5) Broom is a compound machine.
1) True
2) False
3) True
4)True
5) False
Which internal forces is represented in each of the examples listed below?
a) Ripping a piece of paper towel off the paper towel roll.
b) Pulling on ropes to set up a tent.
c) Twisting the lid off a container.
d) Squeezing the tyre of a bicycle to check its pressure.
e) Wringing out a wet dishcloth
A) Shear
B) Tension
C) Torsion
D) Compression
E) Torsion
Name the most obvious external force acting on the structure. What is the direction of this force?
Gravity; It always acts downwards that's how everything is hold to the ground.
What is the science behind the working of a simple machine?
Simple machine help us change the direction of the force applied and also overcome a larger force using a smaller force.
For example: 1 -When we use a lift, we are using a pulley.
2 -When we cut something with a knife, we are using a wedge.
Write simple machines used in given compound machines.
a) Fishing rod
b) Crane or Tow truck
c) Clippers
d) Escalator
e) Hand Drill
A) Pulley, Wheel & Axle, and Fulcrum(Lever)
B) Pulley, Lever and Wheel & Axle
C) Lever and Wedges
D) Pulleys (Inside) and Inclined Plane
E) Screw and Wheel & Axle