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4 March, 04:50

3 In a television tube, an electron starting from rest experiences a force of 4.0 * 10-15 N over a distance of 50 cm. The final speed of the electron is (do not worry about relativistic effects) :

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  1. 4 March, 05:11
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    The final speed of the electron = 2.095*10⁸ m/s

    Explanation:

    From newton's fundamental equation of dynamics,

    F = ma ... Equation 1

    Where F = force, m = mass of the electron, a = acceleration of the electron.

    making a the subject of the equation,

    a = F/m ... Equation 2

    Given: F = 4.0*10⁻¹⁵ N,

    Constant: m = 9.109*10⁻³¹ kg.

    Substituting into equation 2

    a = 4.0*10⁻¹⁵/9.109*10⁻³¹

    a = 4.39*10¹⁶ m/s².

    Using newton's equation of motion,

    v² = u²+2as ... Equation 3

    Where v = final velocity of the electron, u = initial velocity of the electron, a = acceleration of the electron, s = distance covered by the electron.

    Given: u = 0 m/s (at rest), s = 50 cm = 0.5 m, a = 4.39*10¹⁶ m/s²

    Substituting into equation 3

    v² = 0² + 2 (0.5) (4.39*10¹⁶)

    v = √ (4.39*10¹⁶)

    v = 2.095*10⁸ m/s

    Thus the final speed of the electron = 2.095*10⁸ m/s
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