Question

A motorist driving at 25 meters/second decelerates to
15 meters/second. The combined mass of the vehicle and the driver is 1.5 × 10³ kilograms. What is the amount of mechanical work done by the vehicle?

Answer 1

Work done = change in energy = 0.5*m*v1*v1 - 0.5*m*v2*v2
\[\frac{ 1 }{ 2 } m \left( v_i^2 - v_2^2 \right) = \frac{1}{2} 1.5 \times 10^3 \left(25^2 - 15^2 \right) = 300 \times 10^3 N\]

Answer 2

i get it now, but how would i work this out?

An object having a mass of 2.0 kilograms falls from a height of
15 meters. What is its kinetic energy when it hits the ground?

Answer 3

Gain in kinetic energy = loss in potential energy = m*g*change in height
\[mg \Delta h = 2 * 9.8 * \left( 15 - 0 \right) = 294\]

Answer 4

thanks, i just passed my test haha

Answer 5

@lycan1995 though I had made this aware to admins/mods but I am still requesting you :

This site only helps those people who are keen to help themselves first.. I actually mean to say that you must have tried that first... Oh k so leave this now,, the main point is:

This site does not help the users fort the tests... they should attempt them themselves...

I hope you got my point though if you need more information consider:

http://openstudy.com/code-of-conduct

Also since you are a new user :

Welcome to this world of education \(\huge{\color{blue}{\cal{OpEnStUdY}}}\)

Answer 6

@lycan1995 I have to agree with @mathslover .
Please don't use OpenStudy to cheat on your tests in the future.