Work, energy and simple machines A2 20-31
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What are contact forces?
They act when surfaces are in contact.
Name some examples of contact forces
• Air resistance • Friction
What are drag forces?
The force that slows down an object moving in a fluid, as it has to push the fluid to move.
Name some examples of drag forces.
• Water resistance • Air resistance
Name 2 things that an object does when the resultant force is zero.
• It stops moving • It moves in the same direction in a constant speed.
What is deformation
Forces changing the shape of an object.
What is caused by forces streching an object?
Tension
What is caused by forces squashing an object?
Compression
how would reaction force work?
When you apply force on something, your weight pushes particles together, cuasing the bonds to get compressed, then they push back and support you. That support created is called the Reaction Force
What is meant by an extension in stretching.
The amount a material stretchs from its original position.
What is an Elastic limit
The limit of how much an elastic object can stretch until it physically cannot return back to its original state.
How does Hookes Law work
When the object’s extension doubles when you double the force it obeys Hooke’s Law.
What is Moment?
The turning force on a object.
What is the formula to calculate moment?
Force (N) x Distance from the pivot (m) = Moment (Nm)
What do you mean when an object is in equilibrium.
The sum of clockwise moment is equal to the sum of the anticolockwise moments.
How is fluid pressure produced?
Gases and Liquids (fluids) have atoms and molecuels that collide against surfaces to produce fluid pressure.
What is the equation for calculating fluid pressure
Force (N) / Area (m2) = Fluid Pressure (N/m2)
How can you increase gas pressure?
• Heat the gas • Squash the gas
Define atmospheric pressure.
Pressure exerted by the weight of the air around you.
Why does atmospheric pressure decrease as altitude increases?
There are less air molecules, as they get pulled lower towards earth’s gravity.
Define liquid pressure
Pressure exerted by aliquid on a specific area.
Why are liquids incompressible?
There a very little gaps between liquid particles unlike gas particles.
Why is the wall of a dam not straight?
Because the liquid pressure is greater at the bottom, so the wall curves outwards.
How does upthrust in water work?
When an object is submerged in water, the liquid pressure under the objetc is greater than the pressure over it. So, the object is pushed upwards because the depth of the lower side is higher than the upper side.