Answer:
A) 
B) 
Explanation:
Given:
mass of car, 
A)
frequency of spring oscillation, 
We knkow the formula for spring oscillation frequency:




Now as we know that the springs are in parallel and their stiffness constant gets added up in parallel.
<u>So, the stiffness of each spring is (as they are identical):</u>



B)
given that 4 passengers of mass 70 kg each are in the car, then the oscillation frequency:



The stopwatch will be the most useful in determining the kinetic energy of a 50 g battery- powered car traveling a distance of 10 m.
<h3>What is kinetic energy?</h3>
Kinetic energy is the energy of a body possessed due to motion.
This means that for an object to possess kinetic energy, it must be in motion.
The kinetic energy is measured in Joules, which is a product of the mass of the substance and the time taken to travel a distance.
A stopwatch is an instrument used to measure time as one of the components of kinetic energy.
Therefore, the stopwatch will be the most useful in determining the kinetic energy of a 50 g battery- powered car traveling a distance of 10 m.
Learn more about kinetic energy at: brainly.com/question/12669551
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