Physics Term 1 Flashcards
How do you read Vernier Callipers?
- Close the callipers and record any zero error
- Put object either inside or outside jaws and close them (outside jaws if measuring inside of an object, inside jaws if measuring outside)
- Read the main scale
- Read Vernier scale by matching up line and add onto the reading from the main scale
- Subtract/Add zero error
How do you read a Micrometer Screw Gauge
- Close the screw gauge by turning the thimble, followed by the ratchet until it starts to click and record the zero error
- Open the screw gauge, put the object between the anvil and spindle and gently close the screw gauge by turning the ratchet until it clicks
- Read the main scale followed by the thimble scale
- Record the final reading by adding or subtracting the zero error
List the SI units
Time - seconds Length - metres Amount of Substance - mole Mass - kilogram Current - amperes Temperature - kelvin Light Intensity - candela
List the prefixes
giga (G) = 10^9 mega (M) = 10^6 kilo (k) = 10^3 hecto (h) = 10^2 deka (da) = 10^1 deci (d) = 10^-1 centi (c) = 10^-2 milli (m) = 10 ^-3 micro(μ) = 10^-6 nano (n) = 10^-9 pico (p) = 10^-12
Define accuracy
Accuracy is the measure of how close your measurements are to the true or accepted value.
What two things does precision describe about your measurements?
- Repeatibility
2. The number of decimal places given for your measurement
What is the formula for absolute error & percentage error?
Absolute Error = measured value - accepted value
Percentage Error = (error in measurement / accepted value) x 100
Define mass
Mass is the measure of a body’s inertia (its ability to resist changes in its acceleration. Mass is measured in kilograms. Mass does not change with location in the universe.
Define weight
Weight is the effect of a gravitational field on a mass. Weight is a force measured in Newtons, N.
What is the formula for weight?
weight (Newtons, N) = mass (kilogram, kg) x gravitational field strength (N kg^-1)
w = mg
Define density
Density is defined as mass per unit volume of a substance. The standard units are kg / m^3 or g/cm^3. Remember 1 ml = 1 cm^3
What is the formula for density?
density = mass / volume
ρ = m / v
Define scalars and vectors
A scalar has a magnitude (size) only. A vector has both magnitude and direction. Time, Speed, Energy, Mass & Distance are all scalar quantities. Acceleration, Velocity, Momentum, Force, Weight & Displacement are vector quantities.
What is the formula for average speed?
Average speed = distance travelled / time taken, the unit for average speed is m/s
Define displacement
The distance moved in a stated direction.
What is the difference between velocity and speed?
Velocity is the distance travelled in a unit time in a stated direction, whereas speed is just the distance travelled in unit time.
What is the formula for velocity
Velocity = displacement / time taken
Define acceleration
The change in the velocity in unit time.
What is the formula for acceleration?
Acceleration = change in velocity / time taken. a = (v - u)/t
What is the gradient of a distance - time graph used to represent?
It represents the speed
What is the gradient of a velocity - time graph used to represent?
Acceleration
How do you calculate displacement in a velocity - time graph?
By finding the area under the graph.
State the variables in the s u v a t equations
u = initial velocity v = final velocity t = time s = displacement a = constant value of acceleration
State the 5 s u v a t equations
v = u + at v^2 = u^2 + 2as s = 1/2(u + v)t s = ut + 1/2at^2 s = vt - 1/2at^2
Define a force
A force is a push or pull. It can cause a change in the body’s shape, speed or direction.
What is a force arrow and what does this arrow show?
A force arrow is an arrow used to represent a force. The arrow shows the size of the force (the longer the arrow, the bigger the force) and also in which direction the force acts.
State Newton’s first law
A body’s motion will remain at rest or in uniform motion unless acted upon by an external unbalanced force.
State Newton’s second law
This can be simplified to F = m x a, where F is the resultant force on an object. However correctly stated, the formula should be F = dp / dt.
State Newton’s third law
When a force acts on an object, another force of the same type, equal in size but opposite in direction acts on an object (i.e. every action has an opposite and equal reaction)
State Hooke’s law
Extension of a spring is directly proportional to the stretching force applied. This is only true if the limit of the proportionality of the spring is not exceeded.
F ∝ x or F = kx. The force constant k tells us how stiff the string is.
What are the two conditions for equilibrium?
- The sum of the forces in all directions must be equal to zero (i.e. no resultant force)
- The sum of all moments about any point must be equal to zero (i.e. clockwise moments equal anticlockwise moments)
State the formula for centripetal force
F = mv^2/r
= m x w^2 x r
State the formula for acceleration in circular motion
a = v^2/r
State the formula for angular velocity
w = 2πf
= 2π/T
State the formula for tangential velocity
v = wr
Define moment
The turning effect of a force. Moment depends on the size (magnitude) of the force & the perpendicular distance between the line of action of the force and the turning point (pivot)
State the formula for torque
Moment = Force x Perpendicular distance M = Fd , measured in Nm
What is the centre of mass?
The point through which the mass of an object appears to act
How do you know if a body is stable?
A body is stable if, when tilted slightly, the line of action of its weight passes through its base.
What is the formula for momentum?
Momentum = mass x velocity p = mv, measured in kg m/s
Correctly state Newton’s second law
The rate of change of momentum of an object is proportional to the resultant force acting on the object and is in the direction of the force.
State the formula for force in momentum
Force = change in momentum (kg m/s) / time taken for the change
= final momentum - initial momentum / time
taken for the change
State the formula for impulse
Impulse = force x time, it is equal to the change in momentum. The unit is Newton Seconds
State the law of conservation of momentum
the total momentum before the collision = total momentum after collision
m1 x u1 + m2 x u2 = m1 x v1 + m2 x v2
Define pressure
The force per unit area acting perpendicular to a surface. Measured in pascals (Pa) or newtons/metre^2.
1 Pa = 1 N/m^2
State the equation for pressure
Pressure = force / area P = F/A
State the equation for fluid pressure
Pressure = depth x density x gravitational field strength P = h ρ g
What is the atmospheric pressure?
1.01 x 10^5 Pa or 1 atmosphere (1 atm) or 760 mm Hg
