How much work must be done on a 5-kg snowboard to increase its speed from 2 m/s to 4 m/s?
a. 22.5 j
b. 40 j
c. 30 j
d. 15 j

Option C = 30 j

Explanation:

Given data:

mass of snowboard = 5 Kg

Initial speed = 2 m/s

final speed = 4 m/s

work done = ΔE= ?

ΔE= change in kinetic energy

Solution:

Formula:

K.E (initial) = 1/2 × mv²

K.E (initial)  = 1/2 × 5 Kg . (2m/s)²

K.E (initial) = 1/2 × 20 Kg.m²/s²

K.E (initial) = 10 Kg.m²/s² or 10 J      

   Kg.m²/s² = J

K.E (finial) = 1/2 × mv²

K.E (finial) = 1/2 ×  5 Kg . (4m/s)²

K.E (finial) = 1/2 ×  5 Kg . 16 m²/s²

K.E (finial) = 1/2 × 80 Kg.m²/s²

K.E (finial) = 40 Kg.m²/s²  or 40 J

work done =  ΔE = K.E (finial) - K.E (initial)

work done =  ΔE = 40 J - 10 J

work done =  ΔE = 30 J