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Motion In Straight Line

Question

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Two similar charges having mass m and 2m are placed in an electric field. The ratio of their kinetic energy is :

4:1

1:1

2:1

1:2

Solution

C.

2:1

Force on charged particle is electric field F = q E

$Acceleration a = \frac{F}{m} = \frac{q E}{m} Velocity v = u + a t = 0 + \frac{q E}{m} t u - initial velocity, v - final velocity So kinetic energy K = \frac{1}{2} {mv}^{2} K = \frac{1}{2} m {(\frac{q E}{m} t)}^{2} Ratio of kinetic energies = \frac{\frac{1}{2} m_{1} {(\frac{q E}{m_{1}} t)}^{2}}{\frac{1}{2} m_{2} {(\frac{q E}{m_{2}} t)}^{2}} = \frac{m_{2}}{m_{1}} = \frac{2 m}{m} = \frac{2}{1} Ratio of kinetic energies = 2 : 1$

Some More Questions From Motion in Straight Line Chapter

Is absolute rest or absolute motion possible?

What is the most essential thing to study the motion of a body?

Can a body be always at rest in some frame?

Can a body be in motion in the frame associated with the body itself?

When an object in motion can be considered as particle or point object?

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Can a train be taken a particle? Give an example in support of your answer.

A particle is moving along curved line in space. Is the motion one dimensional?

State which of the following are examples of one, two or three dimensional motion:

(a) A kite flying in the sky.

(b) The earth revolving around the sun.

(c) A train moving along the equator of the earth in clockwise direction.

(d) Accelerated motion of a particle in a straight line.

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