Physical quantities and measurement techniques
14 flashcards to master Physical quantities and measurement techniques
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Describe how you would accurately measure the length of a small metal rod using a ruler, minimizing parallax error.
1. Place the ruler alongside the metal rod.
2. Ensure the ruler is aligned parallel to the rod to avoid skew measurements.
3. Place the zero mark of the ruler at one end of the rod.
4. Read the value on the ruler where the other end of the rod aligns.
5. Position your eye directly above the reading to avoid parallax error (looking at an angle will give a false reading). Record this value as the length.
A student uses a measuring cylinder to find the volume of 10 identical marbles. State three precautions they should take to obtain an accurate measurement.
1. Ensure the measuring cylinder is placed on a flat, level surface to avoid a tilted reading.
2. Read the meniscus at eye level to avoid parallax error.
3. Before adding the marbles, record the initial water volume in the cylinder.
Describe how you would accurately measure the time it takes for a pendulum to complete 10 full swings using a stopwatch.
1. Start the stopwatch as the pendulum is released for its first swing.
2. Count the number of complete swings (1 full swing = there and back).
3. Stop the stopwatch after 10 complete swings.
4. Divide the total time recorded on the stopwatch by 10 to find the average time for one swing. This reduces error.
A student uses a digital timer to measure the time for a ball to roll down a ramp. They perform three trials and record the following times: 2.1 s, 2.2 s, and 2.7 s. State one way the student could improve the accuracy of their measurement.
The student could perform more trials and calculate the average time. This will reduce the impact of random errors.
A pendulum completes 20 oscillations in 36 seconds. Calculate the average period of one oscillation.
Period (T) = Total time / Number of oscillations
T = 36 s / 20
T = 1.8 s
The period is found by dividing the total time by the number of oscillations. This gives a more accurate value than timing just one swing.
State why it is more accurate to measure the time for multiple oscillations of a pendulum when determining the average period, rather than measuring just one oscillation.
Measuring multiple oscillations reduces the percentage error caused by the reaction time when starting and stopping the timer. The error is spread over a larger time interval, thus reducing its impact on the final calculated period. Also helps to reduce systematic errors.
State whether each of the following physical quantities are scalar or vector: displacement, energy, force, mass, speed, velocity.
Scalar quantities: energy, mass, speed.
Vector quantities: displacement, force, velocity.
Scalar quantities only have magnitude; vector quantities have both magnitude and direction.
A car travels 200 m North, then 150 m East. Explain why the total distance travelled by the car is different from the magnitude of the car's overall displacement.
Distance is the total length of the path travelled. Displacement is the straight-line distance from the starting point to the ending point, along with the direction.
Distance = 200 m + 150 m = 350 m. Distance is a scalar quantity.
Displacement = √(200² + 150²) = 250 m. Since displacement considers direction, it is calculated by a straight line rather than the overall distance travelled. Displacement is a vector quantity.
State three scalar quantities.
1. Distance
2. Time
3. Mass
Scalar quantities are defined by magnitude only, not direction.
A car travels a distance of 120 m in 4 s. Energy transferred in this time is 2400J. Which of these quantities is a scalar quantity?
Distance, Time and Energy are all scalar quantities. They are defined by magnitude only and do not have a direction.
State four vector quantities.
1. Force
2. Velocity
3. Acceleration
4. Momentum
A vector quantity has both magnitude and direction.
A car accelerates from rest to a velocity of 20 m/s East in 5 seconds. Explain why velocity is a vector quantity, while speed is a scalar quantity.
Velocity is a vector quantity because it specifies both the magnitude (20 m/s) and direction (East). Speed, on the other hand, only provides the magnitude (20 m/s) and does not include any directional information. Therefore, speed is a scalar quantity.
A boat travels east across a river at 3.0 m/s. The river current flows south at 4.0 m/s. Calculate the magnitude of the boat's resultant velocity.
1. Formula: v = √(v_east² + v_south²)
2. Substitution: v = √(3.0² + 4.0²)
3. Calculation: v = √(9 + 16) = √25 = 5.0 m/s
*Explanation: The boat's eastward velocity and the river's southward velocity are perpendicular vectors. The resultant velocity is the hypotenuse of the right-angled triangle formed by these two vectors.*
A force of 9.0 N acts horizontally on an object. A second force of 12.0 N acts vertically upwards on the same object. Describe how you would determine the direction of the resultant force.
1. Diagram: Draw a right-angled triangle. One side represents the 9.0 N horizontal force, and the other represents the 12.0 N vertical force.
2. Trigonometry: Use trigonometry (specifically, the tangent function) to find the angle (θ) between the horizontal and the resultant force. tan(θ) = opposite/adjacent = 12.0/9.0
3. Calculate: θ = tan⁻¹(12.0/9.0) ≈ 53.1°
4. Direction: State the direction as approximately 53.1° upwards from the horizontal.
Key Questions: Physical quantities and measurement techniques
State whether each of the following physical quantities are scalar or vector: displacement, energy, force, mass, speed, velocity.
Scalar quantities: energy, mass, speed.
Vector quantities: displacement, force, velocity.
Scalar quantities only have magnitude; vector quantities have both magnitude and direction.
State three scalar quantities.
1. Distance
2. Time
3. Mass
Scalar quantities are defined by magnitude only, not direction.
State four vector quantities.
1. Force
2. Velocity
3. Acceleration
4. Momentum
A vector quantity has both magnitude and direction.
About Physical quantities and measurement techniques (1.1)
These 14 flashcards cover everything you need to know about Physical quantities and measurement techniques for your Cambridge IGCSE Physics (0625) exam. Each card is designed based on the official syllabus requirements.
What You'll Learn
- 3 Definitions - Key terms and their precise meanings that examiners expect
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