Question

1) the energy associated with an electron of velocity 10^6 m/s is ______?
A.4.5*10^-10
B.4.5*10^-19
C.3*10^-10
D.3*10^-19

2) the momentum of a particle is numerically equal to its kinetic energy . What will be the velocity of the particle ?(explain with the formula )
A.4m/s
B.1m/s
C.2m/s
D. None

3)what is the weight of a 700g of a body on a planet whose mass is 1/7th of that of earth and radius is 1/2 of earth ? (Explain with the formula ?
A.400g
B.700g
C.300g
D.500g ??

Need solutions to each , quick !!

Answer 1

1.  KE = 1/2 m v² = 1/2 * 9.1 * 10⁻³¹ * (10⁶)² = 4.55 * 10⁻¹⁹ J

2. m v = 1/2 m v²
    So  v = 2 units

3.  On Earth:  W₁ = GM₁ m/R₁²  = m g,
     On other planet:    W₂ = GM₂ m/R₂²
            = g R₁²/M₁  * M₂ m/R₂²
     W₂ = g * 2² * 1/7 * 0.700 = 0.400 g   Newtons