Other Physics Answers

a) Calculate the cut-off wavelength for aluminium, which has a work function of

4.08 eV. Will photo electrons be emitted when radiation of wavelength 400 nm is

incident on an aluminium surface?

(b) Calculate the de Broglie wavelength of a non-relativistic proton with a kinetic

energy of 10 eV.

(c) An excited state in an atom has a life time of Calculate the line 3.0 x10^-7s

width of the emitted photon, when the atom decays spontaneously to its ground

state.

(c) The speed of a particle relative to an observer on the Earth is 0.80c, and the

speed of another particle relative to her is -0.90c. What is the speed of the

particles with respect to each other?

(d) A particle of rest mass 1.0 kg has an initial speed of 1.0x10⁸ ms^-1 A constant

relativistic force of magnitude 5.0 x 10⁶N is exerted on the particle in the same

direction as the initial relativistic momentum for 100 s. Calculate the magnitudes

of the initial and final relativistic linear momenta of the particle.

(e) Calculate the linear momentum, kinetic energy and total energy (in J and MeV) of

a particle travelling with speed 0.90c given that its rest mass is and 1.68 x10^-27kg and 1MeV =1.6 x10^-13 J

a) Two observers observe two events from different inertial frames of

reference in uniform relative motion at a speed of 0.90c. Under what condition

would the observers observe these events to be simultaneous? Write down

all possible conditions under which the events would not be simultaneous for the

two observers.

(b) The mean lifetime of a particle is 2.5 micro second when it is produced in the top layers of the Earth’s atmosphere. If it travels at the speed of 0.9999c, what is its life time

as measured by an observer on the Earth? Calculate the distances travelled by the particle in its own frame of reference and the Earth’s frame of reference.

The density of iron is 7860 kg/m^3 what is the mass of an iron sphere whose diameter is 0.50 m

7. The first resonant length of a closed air column occurs when the length is 40 cm. What will the third resonant length be? 

8. A police car with a siren that has a frequency of 900 Hz is moving toward you at 32.0 m/s. Given that the speed of sound is 340 m/s, what is the apparent frequency you hear?

1. A pendulum has a mass of 2.35 kg. If the pendulum swings back and forth 110 times in 90.0 seconds, what is the length of the pendulum?

2. A vertical spring is stretched 60.0 cm by a hanging 5.00 kg mass.

a. What is the spring constant?

b. What will be the frequency of vibration of this spring system? 

4. Determine the acceleration of a pendulum bob as it passes through an angle of 15 degrees to the right of the equilibrium point.

5. Radio telescopes receive waves from distant stars. If such a wave has a wavelength of 24 cm and travels at the speed of light (c = 3.00 x 108 m/s), what is the frequency?

6. The speed and wavelength of coastal water waves are 4.0 m/s and 6.0 m respectively. When the waves enter a shallower region, the speed decreases to 1.7 m/s. What is the wavelength in the shallower region?

The amplitude of vibration of a monarch butterfly's wings is 1.5 cm. If the frequency of vibration of the wings is 9.0 Hz, through what distance, in metres, do the wing tips travel in 1.0 min? [1A, 4T]

A sonometer wire of l vibrates at a frequency of 350hz when the length of the wire is increased by 15cm the wire vibrates at 280hz under constant tension determine l