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describe how a microwave oven works (EM waves + thermal physics)

microwaves are Electromagnetic waves with a wavelength in the order of 10^-6m (the prefix for 10^-6 is micro, just as 10^-3 is milli). these short wavelength waves have a high energy due to equation E=hc/ λ ...
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Answered by Andrew E. • Physics tutor
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A car of mass m is travelling at a speed v around a circular track of radius r banked at an angle θ. (a) What is the centripetal acceleration of the car? (b) What is the normal force acting on the car? (c) If θ = 45°, r = 1 km what is the maximum speed?

(a) The formula for the centripetal acceleration of an object undergoing circular motion at a radius r and speed v is a = v^2/r so as F = ma the centripetal force is F = mv^2/r. 2 marks By drawing a diagram,...
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Answered by Jack M. • Physics tutor
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In an electric propulsion system, alpha particles are accelerated through a potential difference of 100kV at an average rate of 10^20 alpha particles per second. Calculate the average thrust the system can provide.

Take the mass of alpha particle to be 6.64 10^-27 kg accurate to 3 s.f. Note that the the work done in an electric field accross a potential difference is E = QV, where Q is the total charge of the alpha par...
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Answered by Alexandru A. • Physics tutor
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A bullet is fired horizontally from a gun at a height of 1.5m at 280m/s. Calculate the time taken for it to hit the ground. A second bullet is fired from an adjacent gun at 370m/s. Calculate the distance it travel before the first bullet hits the ground.

Time for first bullet to hit ground: s = -1.5m, u = 0ms -1 , v = ?, a = -9.81ms -2 , t = ?.s = ut + 1/2(at 2 )-1.5 = 0 + 1/2(-9.81 t 2 )9.81t 2 = 1.5 2 = 3t = sqrt(3/9.81) = 0.55s (2s.f.)Distance travelled b...
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Answered by Ayush N. • Physics tutor
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During take-off from earth, an astronaut of mass 76kg has an area of contact with his seat of 0.095m^2. Calculate the average pressure on the seat when the upward acceleration of the rocket is 47ms^-2

There are two parts to this question that we should consider seperately: Firstly, we need to work out the total thrust force that is being applied through the seat onto the astronaut. Critically, this is the...
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Answered by Oliver N. • Physics tutor
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