How Much Work is Required to Accelerate a Mass from 2 m/s to 60 m/s?

[Ockonal]

Homework Statement

What work needs to be done to change body speed with mass 6×10⁴ kg from 2 m/s to 60 m/s?

Homework Equations

A = mgh
A = FS
A = mv²/2

The Attempt at a Solution

A₁ = mV₁² / 2
A₂ = mV₂² / 2
A_res = A₂ - A₁;

A_res = m/2 × (V₁² - V₂²)
A_res = 3×10⁴ × (4 - 3600)

The result is negative and too big. Is that right?

 

[Andrew Mason]

Homework Statement

What work needs to be done to change body speed with mass 6×10⁴ kg from 2 m/s to 60 m/s?

Homework Equations

A = mgh
A = FS
A = mv²/2

The Attempt at a Solution

A₁ = mV₁² / 2
A₂ = mV₂² / 2
A_res = A₂ - A₁;

A_res = m/2 × (V₁² - V₂²)
A_res = 3×10⁴ × (4 - 3600)

The result is negative and too big. Is that right?

The change in kinetic energy is positive: \Delta KE = \Delta (mv^2/2) = .5m(v_2^2-v_1^2)

What units does your answer have? Why do you think the result is too big?

AM

 

[Ockonal]

Ok, nevermind. Solved it, thanks.

 

[ashishsinghal]

A_res = m/2 × (V₂² - V₁²)