SOLUTION: Can someone please help me with this problem: The speed of a 4000-kg truch whose KE is 1.8 MJ is: a. 0.95 m/s b. 30 m/s c. 94 m/s d. 900 m/s

Question 190776: Can someone please help me with this problem:
The speed of a 4000-kg truch whose KE is 1.8 MJ is:
a. 0.95 m/s
b. 30 m/s
c. 94 m/s
d. 900 m/s
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
I'm assuming that you've been given the kinetic energy formula: where "KE" is the kinetic energy (think of it as the energy it has when it is moving), "m" is the mass, and "v" is the velocity

Note: the units for the three variables are:

KE: joules (j)
m: kilograms (kg)
v: meters per second (m/s)

the units in this problem are very important

First, take note that 4000 kg in scientific notation is written as kilograms

Also, 1.8 MJ (1.8 megajoules) can be written as 1,800,000 joules, which is joules. So the kinetic energy is joules.

Start with the given formula

Plug in and

Multiply by to get

Divide both sides by .

Divide

Rearrange the equation

Take the square root of both sides (we're only interested in the positive square root)

Take the square root of 900 to get 30

So the velocity is 30 m/s
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