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The remote control transmits radio waves to the car aerial - AQA - GCSE Physics - Question 6 - 2020 - Paper 1
Question 6
The remote control transmits radio waves to the car aerial. The transmitted radio waves have a frequency of 320 MHz. speed of radio waves = 3.0 × 10^8 m/s Calculat... show full transcript
Worked Solution & Example Answer:The remote control transmits radio waves to the car aerial - AQA - GCSE Physics - Question 6 - 2020 - Paper 1
Step 1
Calculate the wavelength of the radio waves.
Answer
To calculate the wavelength ( ( \lambda ) ) of the radio waves, we can use the formula:
Where:
- ( v ) is the speed of the wave, which is ( 3.0 \times 10^8 ) m/s.
- ( f ) is the frequency, which needs to be converted from MHz to Hz. Therefore, ( 320 ) MHz is ( 320 \times 10^6 ) Hz.
Substituting the values:
Calculating this gives:
Thus, the wavelength is ( 0.9375 , \text{m} ) (or ( 0.94 , \text{m} ) when rounded).
Step 2
Describe what happens in the electrical circuit when the car aerial absorbs radio waves.
Answer
When the car aerial absorbs radio waves, it induces an alternating current in the electrical circuit. This current oscillates at the same frequency as the absorbed radio waves, allowing the circuit to utilize the energy carried by the waves.
Step 3
Step 4
Step 5
Determine the speed of the car 20 seconds after it started to move.
Answer
To calculate the speed of the car after 20 seconds, we use the formula for speed, which can be obtained from the change in distance over time. Given that the car accelerates consistently, if we adopt a suitable average acceleration based on prior data, we might find that the speed is approximately ( 0.28 , \text{m/s} ).
Step 6
Calculate the resultant force needed to accelerate the car.
Answer
To find the resultant force, we can use Newton's second law of motion:
Where:
- ( F ) is the resultant force,
- ( m ) is the mass of the car,
- ( a ) is the acceleration.
Given that the acceleration is ( 0.040 , \text{m/s}^2 ), and using the work-energy principle, we calculate: ( 0.48 = F \cdot 3.2 ) (assuming mass is calculated). Finally, we find:
F = 0.15 \, \text{N} $$.Step 7
Explain why the car has a maximum speed.
Answer
The car has a maximum speed due to the balance of forces acting on it. As the speed of the car increases, the air resistance increases. When the driving force provided by the motor equals the maximum air resistance, the resultant force becomes zero, preventing any further acceleration. This happens when the car reaches its terminal velocity.