Question

How much work must be done on a 5 kg snowboard to increase its speed from 2 m/s to 4 m/s

Answer 1

Answer:

a) 30J

Explanation:

use formula first find K.E with both speeds

K.E. = 1/2 m v2

and then

work done= change in kinetic energy

Answer 2

30 Joule of work is to be done.

Option: a

Explanation:

Given, mass of snowboard = 5 Kg

Initial speed = 2 m/s,  Final speed = 4 m/s, Work done = ΔE

Where, ΔE= change in kinetic energy  

Solution:

$\text { Kinetic Energy (initial) }=\frac{1}{2} \times \mathrm{mv}^{2}$

$\text { Kinetic Energy (initial) }=\frac{1}{2} \times 5 \mathrm{Kg} \times(2 \mathrm{m} / \mathrm{s})^{2}$

$\frac{1}{2} \times 20 \mathrm{Kg} \cdot \mathrm{m}^{2} / \mathrm{s}^{2}$ = $10 \mathrm{Kg} \cdot \mathrm{m}^{2} / \mathrm{s}^{2}$

$\text { Kinetic Energy (final) }=\frac{1}{2} \times m v^{2}$

$\frac{1}{2} \times 5 \mathrm{Kg} \times(4 \mathrm{m} / \mathrm{s})^{2}$

$\frac{1}{2} \times 5 \mathrm{Kg} \times 16 \mathrm{m}^{2} / \mathrm{s}^{2}$

$\frac{1}{2} \times 80 \mathrm{Kg} \cdot \mathrm{m}^{2} / \mathrm{s}^{2}$

$40 \mathrm{Kg} \cdot \mathrm{m}^{2} / \mathrm{s}^{2}$

Work done = ΔE = Kinetic Energy (final) - Kinetic Energy (initial)  

Work done = ΔE = 40 J - 10 J work done = ΔE = 30J