A particle of mass 2 mg moves with constant speed and is found to pass two points 5.0 m apart in a time interval of 5 ms. The kinetic energy of the particle is 

Options

A. `1.0 J`
B. `2.0 J`
C. `3.0 J`
D. `4.0 J`

Answer

A

Explanation

Mass of the particle, `m = 2 mg = 2 xx 10^(-6) kg`
Particle is moving with constant speed, so
Speed, v = `("distance between two points")/("time interval") = (5m)/(5 xx 10^(-3) s) = 10^3 ms^(-1)`
`:.` KE = 1/2 mv^2 = 1/2 (2 xx 10^(-6))(10^(3))^(2) = 1J`