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
