Calculate the frictional force on a 2Kg block resting on a rough ground with μ = 0.7 ?
The frictional force is given as $$F$$=$$μ$$N where N is the normal reaction. N can be calculated by mg where g is acceleration due to gravity N=19.6 Newton and hence $$F$$=19.6*0.7 which is 13.72 Newton. Always remember that unit of force is Newtons
How do we calculate the maxima of a single variable function
To calculate the maxima, we need to differentiate the function with respect to the variable. The value(s) at which the derivative vanishes are the points of interest. Next, you differentiate again and the value(s) at which the double derivative is less than zero are the points at which the function attains a maxima. This procedure can be also extended to multi variable functions
$$How$$ $$can$$ $$something$$ $$behave$$ $$both$$ $$as$$ $$a$$ $$particle$$ $$and$$ $$a$$ $$wave?$$
The answer is in $$Quantum Mechanics$$. If you go into the very microscopic regime and examine the laws of physics, all of these laws translate as some statements in probabilities. The Heisenberg principle on which the Quantum mechanical explanation of the universe rests on is one such example. In this region, particles are described by their corresponding wavefunctions which tell us the probability of it being at a particular place. Hence the particle ceases to be local and is distributed (uniformly or otherwise) in the entire universe. If we scale up these objects that we are explaining ( we get macroscopic) we enter the familiar regime of Classical Physics. Quantum Mechanics is theory that can explain macro as well as micro quite satisfactorily.