Recent content by DrDonaldDuck

Homework Statement "A bullet is fired through a 5.0 cm thick board of some material. The bullet strikes the board with a speed of 200 m/s, and emerges out the other end at 100 m/s.Homework Equations a= (change in velocity)/(change in time) average velocity = .5(initial v + final v)The Attempt...

Someone PLEASE help?!? Growing very desperate here. EDIT: I think I got it. Internal energy=412636J, exhaust heat is the same. So sleepy, please confirm.

Still stumped and don't know how to attack problem!

This is Introductory physics? :O

Wait.. I found out my error! I also had to take in the rotational energy of the ball into account :D /marked as solved

W is the work done and Q is the heat generated. U is the total internal energy. No idea how to do this, hence my non-existent attempt.

Maybe the final velocity is negative? But then there can't be a square root of a negative number. Help!

Homework Statement A heat engine has a carnot efficiency of 0.11. How much internal energy does this engine use in order to do 5.1 x 10^4 joules of work? How much heat does this engine give off/exhaust?Homework Equations (change in)U=Q-W W=(change in)E

My bad. Thanks! Hold on... I used KE(initial) + PE(initial) = KE(final) + PE (final) The initial PE is 0, because the initial height/elevation is 0. so: .5m(3.5m/s)^2 = m(9.8)(.760) + .5m(v)^2. The m's (masses) cancel, but I got 6.125 = 7.448 + .5(v)^2. This must be wrong as I would get a...

The 0.5 is part of the universal equation to find Kinetic energy. Google "Kinetic energy" > Wikipedia entry > "Kinetic energy of rigid bodies" and you will see the equation KE= 0.5mv^2.

Because when the ball reaches the top, it will have gravitational potential energy.

The .5 is in the formula for Kinetic Energy (KE), which is .5mv^2.

Homework Statement "A bowling ball encounters a .760m verticle rise on the way back to the ball rack. Ignore frictional losses and assume the mass of ball is distributed uniformly. Translational speed of ball =3.5 m/s at the bottom of the rise. Find translational speed at the top." -Ball is...