mechanics physics Flashcards
Give examples of scalar quantities
Distance, speed, mass, temperature
Give examples of vector quantities:
Displacement, velocity, force, acceleration
What are the two methods in adding two vectors to find magnitude and direction?
Pythagoras and trigonometry
Scale drawings with resultant vectors
Formula for resolving horizontal component and for vertical component with a vector
x = Vcos()
y = Vsin()
V is vector
x is horizontal component
y is vertical component
`How can you prove a force is in equilibrium
Able to draw a closed triangle
or
Adding horizontal and vertical components so that they equal zero.
Define what is means for an object to be at equalibrium
This is when the sum of all forces acting on it must be zero, therefore must have no resultant force.
Equation of moment
Moment = Force * perpendicular distance
Define a couple:
A couple is a pair of coplanar forces where the two forces are equal in magnitude but opposite in direction
What is the principle of moments
That for an object in equilibrium, the sum of the anticlockwise moments abut a pivot is equal to the clockwise moment
What is the difference between instantaneous velocity and average velocity?
Instantaneous velocity is the velocity of an object at a specific point in time.
Average velocity is the velocity of an object over a specified time frame.
What does the area under an acceleration-time graph represent
The change in velocity
In projectile motion what is independent?
The horizontal and vertical components.
What is the upward force that acts on liquids
Lift
When is terminal speed met?
When all driving forces are equal there is no resultant force.
There is no acceleration so the object moves at constant speed.
State all of newton’s laws:
1 - at constant velocity all objects are at rest or travelling until a resultant force is experienced.
2 - F = ma (force of an object is proportional to its acceleration)
3 - for each force experienced by an object, the object exerts an equal and opposite force.
What is momentum? and the rules regarding it.
The product of mass and the velocity of an object.
Momentum is conserved before and after the collision
According to Newton’s 2nd law: F = ma, a = Change in V/change in time
Therefore F = Change in mass*velocity/ change in time
Proving force is the rate of change in momentum
F * change in time = Change in mass*velocity (rearranged equation)
Impulse = change in momentum
What does the area of a force-time graph indicate?
Change in momentum
What is the unit for impulse
As F * change in time (impulse) = Change in mass * velocity
- the unit is kgms^-1
What are car’s safety design features and how does this help?
Crumple zones, seat belts and air bags increase impact time.
This causes force exerted on passengers to decrease
State the two types of collisions
Elastic - momentum and kinetic energy is conserved
Inelastic - where momentum is conserved and kinetic energy may be transferred to heat, sound
Give an example of inelastic collisions:
Explosions as kinetic energy after the collision is greater.
If objects stick together after the collision it is an inelastic collision,
Define work done:
The force causing a motion multiplied by the distance travelled in the direction of the force
W = FsCos()
Define power
Rate of doing work = the rate of energy transfer
P = W/t
P = Fs/t
Therefore P = Fv
What does the area under a force displacement graph indicate?
Area = work done
