Measurement Uncertainty Quiz (OCR A)

The dimensions of a cube are measured with vernier calipers. The measured length of each side is 30.0 mm.

If the vernier calipers can be read with an uncertainty of +/- 0.1 mm. What is the approximate percentage uncertainty in the value of the volume?

• A) 4%

• B) 3%

• C) 0.3%

• D) 1%

To find the resistivity of a semiconductor, a student makes the following measurements of a cylindrical rod of the material:

length = 25 ± 1 mm,

diameter = 5.0 ± 0.1 mm,

resistance = 68 ± 1 Ω.

The resistivity is calculated to be 53 mΩ·m. What is the uncertainty in this result?

• A) ± 1 mΩ·m

• B) ± 2 mΩ·m

• C) ± 4 mΩ·m

• D) ± 5 mΩ·m

Two students carry out an experiment to determine the ratio of potential difference across two resistors R₁ and R₂ which are connected in series across a low voltage d.c. supply. The resistors have different values such that R₂ = 10 R₁.

The voltmeter used to take the readings gives a reading of 0.2V before any potential difference is applied.

Amy takes one measurement across each resistor and calculates the ratio as V₁ / V₂.

Matthew changes the supply voltage and takes a series of readings for V₁ and V₂. He then plots a graph of V₁ against V₂ and uses the gradient of his graph to determine V₁ / V₂.

Which of the following statements is true?

• Amy's value for V₁ / V₂ will not be affected by the error.

• Amy's value for V₁ / V₂ will be increased because of the error.

• Matthew's value for V₁ / V₂ will not be affected by the error.

• Matthew's value for V₁ / V₂ will be decreased because of the error.

A digital camera records each image as 8 megapixels, with each pixel transferring 14 bits of information.

What is the minimum capacity for a memory card which could hold 120 images?

• 1.7 Mbyte

• 13 Mbyte

• 1.7 Gbyte

• 13 Gbyte

A child (mass m) sits on a car seat which is accelerating horizontally at 0.50g (where g is the acceleration of free fall).

What is the magnitude of the total force F exerted by the car seat on the child?

• A) 0.50 mg

• B) 1.0 mg

• C) 1.1 mg

• D) 1.5 mg

Two metal spheres, A and B, are positively charged. Sphere A is fixed in position. Sphere B is suspended by an insulating thread from a point directly above the center of sphere A as shown in the diagram.

Sphere B has a weight of 0.50 mN. The size of the electrostatic repulsive force is 0.29 mN.

What angle, θ, does the thread suspending sphere B make to the vertical?

• A) 0.66°

• B) 1.0°

• C) 30°

• D) 60°

Each diagram below shows three newton meters, in a two-dimensional arrangement, joined to demonstrate a system of three forces acting at a point. The readings represent the magnitudes of the forces. Which system of forces could be in equilibrium?

• A

• B

• C

• D

The diagram shows the graph of displacement s against time t for an object moving in a straight line.

Which of the following graphs of velocity v against time t represents the motion of the body over this period?

• A

• B

• C

• D

In the absence of air resistance, a stone is thrown from point P and follows a parabolic path, reaching its highest point at T.

The vertical component of acceleration of the stone, as it follows this path, is:

• zero at T

• greatest at T

• greatest at P

• the same at P as at T

A satellite moves at a constant speed in a circular orbit around the Earth.

Which pair of statements about momentum and kinetic energy are correct?

• Momentum constant, Kinetic energy changing

• Momentum constant, Kinetic energy constant

• Momentum changing, Kinetic energy changing

• Momentum changing, Kinetic energy constant