<span>What you need to do while answering this questions, is ask yourself what has cells - only if a thing has cells can you see those cells under a microscope. Objects of animal and plant origin have cells, so blood, plant and cork (made of tree bark) can have cells, and a box too, if it's made of wood. So we can''t exclude any answers based on this. We must then know the story of Robert Hook - and it was in fact a cork. He did this discovery around 1655. At the time his main interest was the microscope rather than the cork, and he used to cork to demonstrate the function of the microscope. The correct answer is CORK.</span>
Given data
*The given 4th harmonic frequency is 31.5 Hz
The fundamental frequency is calculated as

Hence, the fundamental frequency is 7.875 Hz
Suppose car A is moving with a velocity Va, and car b with a velocity Vb,
According the principle of conservation of momentum:
Va x Ma + Vb x Mb = (Ma + Mb) V
V = (Va x Ma + Vb x Mb)/(Ma +Mb)
V = speed of cars after coupling
V = (Va x 20 mg + Vb x 15 mg)/(20 mg + 15 mg)
Put in the values of Va and Vb, and get the V
Answer:
A ball is thrown straight up with a speed of 30
m/s. What is the maximum height reached by
the ball?