An electron and a proton are detected in a cosmic ray experiment, the first with kinetic
energy 10 keV, and the second with 100 keV. Which is faster, the electron or the
proton ? Obtain the ratio of their speeds. (electron mass = 9.11×10-31 kg, proton mass
= 1.67×10–27 kg, 1 eV = 1.60 ×10–19 J).
Given that,
Kinetic energy,
K.E of proton,
K.E is given by,
∴ ratio of their speed is given by,
= 13.54
Thus electron is faster than proton by a magnitude of 13.54.
The bob of a pendulum is released from a horizontal position. If the length of the pendulum is 1.5 m, what is the speed with which the bob arrives at the lowermost point, given that it dissipated 5% of its initial energy against air resistance?
A body of mass 2 kg initially at rest moves under the action of an applied horizontal forces of 7N on a table with co-efficient of kinetic friction 0.1. Compute:
(a) the work done by the applied force in 10 sec.,
(b) the work done by the friction force in 10 sec.,
(c) the work done by the net force on the body in 10 sec.,
(d) the change in kinetic energy of the body in 10 sec and interpret your results.