Question

1)

a) What is the difference between accuracy and precision?

b) What is the difference in resolution between the instruments: Dial Caliper and Micrometer caliper? In order words, what is the lowest division in mm that we can read in each one of these instruments?

c) How do you relate calibration and accuracy? Explain.

2) In the Experiment Newton’s Second Law, explain with your own words, a) the relation that you found between acceleration and mass. What did you keep constant in this part of the experiment? And, b) the relation that you found between acceleration and Force. What did you keep constant in this part of the experiment?

3) In the Experiment Friction, explain with your own words, a) the relation that you found between the maximum static friction force and Normal force, b) the relation that you found between the kinetic friction force and Normal force, and c) How did you get an estimation of the coefficients of static friction and kinetic friction?

4) In the Experiment Work and Power, explain with your own words, a) the concept used to determine the work done to walk or run the flight of stairs, and b) why the calculated Power is the minimum Power needed to walk or run the flight of stairs.

5) In the Experiment Boyle’s Law, explain with your own words, a) the relationship between the absolute pressure of the gas and the Volume of the gas that you found, and b) what is the name of the process of compression of the gas, used in this experiment?

Answer 1

1)

a) Accuracy refers to the closeness of a measured value to a standard or known value. For example, if in lab you obtain a weight measurement of 3.2 kg for a given substance, but the actual or known weight is 10 kg, then your measurement is not accurate. In this case, your measurement is not close to the known value.

Precision refers to the closeness of two or more measurements to each other. Using the example above, if you weigh a given substance five times, and get 3.2 kg each time, then your measurement is very precise. Precision is independent of accuracy. You can be very precise but inaccurate, as described above. You can also be accurate but imprecise.

For example, if on average, your measurements for a given substance are close to the known value, but the measurements are far from each other, then you have accuracy without precision.

A good analogy for understanding accuracy and precision is to imagine a basketball player shooting baskets. If the player shoots with accuracy, his aim will always take the ball close to or into the basket. If the player shoots with precision, his aim will always take the ball to the same location which may or may not be close to the basket. A good player will be both accurate and precise by shooting the ball the same way each time and each time making it in the basket.

b) A Dial Vernier scale on caliper may have a least count of 0.1 mm while a micrometer may have least count of 0.01 mm.

c) Calibration in measurement technology and metrology is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known accuracy, a device generating the quantity to be measured such as a voltage, or a physical artefact, such as a metre ruler.

2)

a) Newton's second law of motion can be formally stated as follows: The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object. a = F/m,

b) The kinetic frictional force is equal to the coefficient of kinetic friction times the normal force.

c) mass is kept constant.

3)

a) Maximum static friction force = coefficient of static friction * normal force (weight)

b) The kinetic frictional force is equal to the coefficient of kinetic friction times the normal force.

c) can be done experimentally. When object just starts moving, Force applied / weight = coefficient of static friction.

when object is moving, {Force applied - (mass*acceleration)} / normal force = coefficient of kinetic friction.

4)

a) Work will be equal to rise in potential energy (whether running or walking) W = m*g*h (h being hieght attained)

Power = work / time taken (time taken while running will be more than while walking, hence power while running will be more )

b) because that amount of potential energy must be attained to rreach that hieght, so that work has to be done

5)

a) Boyle's law is a gas law, stating that the pressure and volume of a gas have an inverse relationship, when temperature is held constant.

b) Isothermal compression because temperature is kept constant.