A bullet of mass 0.010 kg and speed of 100 m/s is brought to rest in a wooden block after penetrating a distance of 0.10 m. The work done on the bullet by the block is
so my answer is 50 but I'm getting it wrong? I don't understand why??
work=KE 1/2(.010)(100)^2=50!
Yes.
Went you slow something down your force is opposite to the velocity, you remove kinetic energy, negative work
well how do I figure how much work the wood block did on the bullet??
The work done is force times distance and that is 500 * 0.1 = 50 Joules which is what you had and I believe is correct either way you do it.
Ok so my professor FINALLY responded to me and said the answer is -50 J not 50J with no explanation.
What variable would I make negative to produce that answer? Would the velocity by negative since the wood is stopping the bullet?
ok! finally some clarity. thank you!
V^2 = Vo^2 + 2a*d = 0,
V^2 = 100^2 + 2a*0.1 = 0,
a = -5*10^4 m/s^2.
F = M*a = 0.01 * (-5*10^4) = -500 N.
W = F*d = -500 * 0.1 = -50 J.
The formula you mentioned, work = KE (kinetic energy), is not applicable in this scenario. Work is defined as the transfer of energy that occurs when a force is applied over a distance.
To calculate the work done on the bullet by the wooden block, you need to consider the force and distance involved. Here's a step-by-step explanation of how to solve the problem:
1. Determine the initial kinetic energy (KE) of the bullet before it's brought to rest. Using the formula KE = 1/2 * mass * (speed)^2:
KE = 1/2 * 0.010 kg * (100 m/s)^2
KE = 50 J (joules)
2. Next, calculate the deceleration of the bullet as it's brought to rest. You can use the equation of motion:
v^2 = u^2 - 2as
where v is the final velocity (0 m/s), u is the initial velocity (100 m/s), a is the acceleration, and s is the distance traveled.
Rearrange the equation to solve for acceleration, a:
a = (u^2 - v^2) / (2s)
a = (100 m/s)^2 / (2 * 0.10 m)
a = 50000 m^2/s^2
3. Now, calculate the force exerted by the block on the bullet using Newton's second law:
F = ma
F = 0.010 kg * 50000 m^2/s^2
F = 500 N (newtons)
4. Finally, determine the work done on the bullet by the block using the formula:
work = force * distance
work = 500 N * 0.10 m
work = 50 J
Therefore, the correct answer is indeed 50 J (joules). It seems like you've made a calculation error or misinterpreted the question. Double-check your calculations to identify where the mistake might have occurred.