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Physics
A Level

Explain why excited atoms only emit certain frequencies of radiation after an electron collides with the atom

  1. Radiation is emitted via photons2) Photon energy is governed by the equation E = hc/wavelength, where h = the Planck constant and c = the speed of light. Both h and c are constants3) Electrons have ...
Answered by Michael H. Physics tutor
4915 Views

I do 400J of work compressing a gas, but I maintain the same temperature. What is the delta U, Q and W in this case?

U = 0Q = -400W = -400

Answered by Helen C. Physics tutor
1814 Views

A trolley of mass 0.75kg is running along a frictionless track at a constant speed of 0.7ms-1, as the trolley passes below a mass of 0.5kg the mass drops a short vertical distance onto the trolley. Calculate the new velocity of the trolley and mass.

Momentum = mass x velocityInitial momentum = 0.75 x 0.7 =0.525kgms-1Momentum is assumed conserved so final momentum = 0.525kgms-1So final mass = 0.5+0.75 = 1.25kgSo final velocity = 0.525/1.25Final veloci...

Answered by Alexander M. Physics tutor
1830 Views

What velocity should your boat have if you want to cross a 72m wide river in 6s by the shortest distance, with a 5 m/s downstream current?

Key physics concepts: Velocity vectors, Distance/speed/time relations Key mathematical concepts: Trigonometry, Pythagorean triples, Vector addition/subtraction.Recall that velocity is a vector

Answered by Physics tutor
1508 Views

A conical pendulum is a mass suspended from a point that traces out a horizontal circle. By balancing the weight with the tension in the string, determine the speed of the bob.

Draw a free-body diagram for the mass with the pendulum suspended at an angle θ to the vertical. The tension in the rope is T and the radius of the circle is r.
Firstly, resolve horizontal forces an...

Answered by Daniel S. Physics tutor
2184 Views

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