Forces In Action Flashcards
Define a force
A force of 1 Newton will give a 1kg mass an acceleration of 1ms⁻² in the direction of the force.
What is weight?
The gravitational force on an object, measured in Newtons.
What is mass
Amount of matter, a base quantity measured in kilograms.
How can you determine weight?
Using a newtonmeter
What is the centre of mass?
The centre of mass of an object is an imaginary point where the entire weight of an object appears at act.
Define centre of ass
A point through which any externally applied force produces straight line motion but no rotation
Determining the centre of gravity:
Make small holes along the edge of the objects made of card.
Insert a pin through one of the holes and hold the pin firmly in a clamp.
Hang a plumb-line from the pin and draw a line along the vertical string of the plumb-line.
Repeat the process for the other holes and the point of intersection is the centre of gravity and centre of mass.
What is drag
A frictional force that opposes the motion of an objects
How does cross- sectional area affect the magnitude of a drag force?
The larger the cross-sectional area results in a greater drag
What is the relationship between drag force and speed?
Drag force is directly proportional to speed²
At the first instant an object starts to fall, what is drag force equal too?
No drag force, the total force is equal to the weight.
As the object falls, its speed increases and what happened to the drag?
The magnitude of drag also increases.
Therefore, net force= mg-D
a =(mg-D)/m
When the object reaches terminal velocity what is the drag force?
The drag force is equal and opposite to the weight.
The object has zero accelerate and speed is constant
Define a moment.
Force times the perpendicular distance of the line of action of force from the axis or point of rotation.
What are the units for moments?
Nm
For a body to be in equilibrium, what conditions are required?
Net force=0
Net moment=0
Define principle of moments.
For a body in rotational equilibrium, the sum of clockwise moments is equal to the sum of anticlockwise moments.
Define the torque of a couple
One of the forces x the perpendicular separation between the forces .
Equation of torque
T= Fd
Define density.
Mass per unit volume
Determine density
Mass can be measured using a digital balance.
For liquids, you can use measuring cylinder to determine the volume.
For irregular solids,add water to a measuring cylinder and then add the object and measure the difference in volume.
How to find the pressure exerted by any vertical liquid?
P= hdg
h= height of the liquid column
d= density of the liquid
g= gravity
Define Archimedes’ principle.
The upthrust exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces.
What is the density of water?
1000kgm-3
Finding the normal force on an inclined plane.
F(N) = mgcos (theta)
Factors affecting the drag on an object?
Speed of object
Shape of object
Roughness/ texture of object
Density of the fluid the object is travelling in
