Topic 2 Flashcards
Equation: SUVAT *
v = u + at
s = ut + ½at²
v² = u² +2as
s = (u+v)t / 2
What is a scalar quantity?
One that only measures magnitude.
What is a vector quantity?
One that measures both magnitude and direction.
How do you find a resultant force using vectors?
Use trigonometry or a scale drawing.
What is an assumption you make when using SUVAT equations?
That acceleration is constant.
How do you solve projectile questions?
Treat horizontal and vertical motion separately.
How does air resistance affect the flight of a projectile?
It is a force which acts against the motion of a projectile, which reduces its speed meaning it doesn’t travel as far.
What does Newton’s 1st Law of Motion state?
A body will remain at a state of constant velocity unless acted upon by an external resultant force.
What does Newton’s 2nd Law of Motion state?
The acceleration is directly proportional to and in the same direction as the resultant force acting upon it.
Equation: Newton’s 2nd Law of Motion *
∑F = ma
∑F = resultant force acting on a body (N)
m = mass of body (kg)
a = acceleration of body (ms⁻²)
What an assumption made when using the equation for Newton’s 2nd Law of Motion?
Mass must be constant.
What is terminal velocity?
The faster you travel, the more air you displace, increasing the opposing force of air resistance which acts against you. When this force has the same magnitude as your thrust/weight, your resultant force becomes zero, and so you travel at a constant velocity.
What does Newton’s 3rd Law state?
For every action there is an equal and opposite reaction.
What are Newton’s 3rd Law pairs?
1) Act on different bodies. 2) The sane type of force. 3) Equal magnitude. 4) Act in opposite directions. 5) Act among the same line.
Equation: Momentum *
p = mv
p = momentum (kgms⁻¹)
m = mass (kg)
v = velocity (ms⁻¹)
Definition: Principle of conservation of momentum
Providing no external forces act on the system, the sum of the initial momentum is equal to the sum of the final momentum.
What is the relationship between the forces exerted on each object during a collision?
No matter the mass of each object, the force each object exerts on the other is of equal magnitude but opposite direction.
Definition: Principle of moments
For a body to be in rotational equilibrium, the sum of the clockwise moments must equal the sum of the anti-clockwise moments, provided that the moments are taken about the same point.
Equation: Moments *
Moment = Fx
F = force (N)
x = perpendicular distance from pivot to line of action of force (m)
Definition: Centre of gravity
The point through which all of the weight of the body appears to act, and the body is in rotational equilibrium.
Definition: Moment
The force times perpendicular distance from the pivot.
(Nm)
Equation: Work *
ΔW = FΔs
ΔW = increase in work done (J)
F = force applied (N)
Δs = distance moved (m)
Equation: Kinetic energy *
Ek = ½mv²
Ek = kinetic energy
m = mass
v = velocity
Equation: Gravitational potential energy *
ΔGPE = mgΔh
ΔGPE = change in gravitational potential energy (J)
m = mass (kg)
g = gravity (N kg-1)
Δh = change in height of centre of gravity (m)
What is the relationship between ΔEgrav and ΔEk?
ΔEgrav = ΔEk
Definition: Principle of conservation of energy
Energy cannot be created or destroyed, just transformed from one form to another.
Equation: Average force
F = ΔW / Δs
F = average force (N)
ΔW = work (J)
Δs = distance (m)
Definition: Work done
The force times distance moves in the direction of applied force.
(J)
What is the relationship between work and energy?
ΔW = Energy
Equation: Power *
P = E / t
P = power (W)
E = Energy (J)
t = time (s)
P = W / t
P = power (W)
W = work (J)
t = time (s)
Definition: Power
The rate at which work is done (or) the rate at which energy is transferred. (W)
Equation: Efficiency *
Efficiency = useful energy output
total energy input
Efficiency = useful power output
total power input
