Module 3 Flashcards
What is displacement?
Displacement is the distance travelled in a particular direction and is a vector quantity, units of metres (m).
What is instantaneous speed?
The speed of an object at a given moment in time, units of metres per second (ms^-1)
What is average speed?
A measure of the total distance travelled in a given time, units of metres per second(ms^-1)
What is velocity?
Displacement per unit time, units of metres per second (ms^-1)
What is acceleration?
The rate of change of velocity and is a vector quantity, units of metres per second squared (ms^-2)
How do you find the velocity from a displacement time graph?
The gradient
What does the gradient of a velocity time graph represent?
Acceleration
How do you find the displacement from a velocity time graph?
Area under the graph
What are the four equations for constant acceleration?
v = u + at
s = ut + 1/2at^2
s=1/2(u+v)t
v^2 = u^2 +2as
What equation is associated with Newton’s Second Law?
Force = Mass x Acceleration (F = Ma). Unit is in Newtons
What is the equation for density?
ρ = m / v (density = mass / volume)
How can you derive the formula for Gravitational Potential Energy?
W = Fd f = ma GPE = mad as a = g and d = h GPE = mgh
Name some techniques and procedures used to investigate the motion and collisions of objects.
Cause a collision between two objects and measure the velocity of the two objects before and after using light gates.
How do you find the elastic potential energy from a force-extension graph?
Calculate the area under the graph
EPE = 1/2(Fx)
State the Archimedes’ Principle.
The upthrust on a body totally or partially immersed in a fluid is equal to the weight of fluid it displaces. p = hpg
State Newton’s 1st Law.
A object remains stationary or travels at a constant velocity in a straight line unless a external force acts on it.
State Newton’s 2nd Law.
The rate of change of momentum of an object is directly proportionally to the net force which acts on the object.
State Newton’s 3rd Law.
If object A exerts a force on object B, then object B will exert an equal but opposite force on object A.
What is the formula for power and its units?
Power = (Force x Distance) / Time
(P = Fd/t)
Power is measured in watts
What are the factors affecting drag?
size, shape, weight, and texture of the surface of an object
Unit of force?
Newton (N) Kgms^-2 (from F=ma)
What is thinking distance?
distance travelled in the time between the driver seeing the danger and pressing the brakes proportional to the velocity
What is braking distance?
distance travelled in the time between the driver hitting the brakes and the car stopping, proportional to the velocity squared
What is stopping distance?
braking plus thinking distance
What is terminal velocity?
when the weight downwards is equal to the drag force upwards
Principle of moments
The sum of the anti clockwise moments is equal to the sum of the clockwise moments in rotational equilibrium
Conservation of momentum
The total linear momentum before a collision is equal to the total linear momentum after a collision, provided no external forces are applied
Couple of forces
Two equal and anti parallel forces, of the same type, acting about a pivot
Torque
The turning effect of a force in circular motion (Force x perp. distance)
Centre of mass
The single point in which all the mass of an object can be assumed to act through
Centre of gravity
The single point in which all the weight of an object can be assumed to act through
Derive KE
W=Fd v^2=u^2+2as
W=kg (nm^-2m) 1/2 v^2=as
W=m(0.5v^2)
KE=1/2mv^2
Derive P=Fv
w=Fd
P=w/t
P=F(d/t)
P=Fv
Derive gpe=mgh
W=Fd
gpe=Fd
gpe=mad
gpe=mgh
Young modulus=?
FL/Ax = stress/strain
p=mv what does this mean?
momentum=mass X velocity
State Hooke’s law
the extension of an object is proportional to the force that causes it, provided that the elastic limit is not exceeded
(f∝x)
A squared + B squared = C [Blank]
Squared
What are the SI units of resistivity?
m^2 S A^-2
What is the unit for work done?
Joules
What is an impulse and what is the unit for it?
the rate of change of momentum.
Define moment
The product of a force and the perpendicular distance of its line of action from the point or axis
Define Torque
The turning moment due to a couple is the product of one of the forces and its perpendicular distance between them.
Units for Torque?
Newton Metres
Centre of Mass
The single point in an object in which all the mass of an object acts can be assumed to be situated
Centre of Gravity
The single point of an object in which gravity is assumed to act upon
Equilibrium
A condition when an object has a total net force of zero (e.g. Thrust - Drag = 0 therefore car is stationary/at constant velocity)
When an object is in equilibrium, what can you do with three forces?
You can create a triangle (closed loop).
Density
Mass per unit volume, kgm^-3
