A lamp is marked 24V, 100W. Describe an experiment to check that the electrical power supplied to the lamp is 100W when the p.d.
1 answer:
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The emerging velocity of the bullet is <u>71 m/s.</u>
The bullet of mass <em>m</em> moving with a velocity <em>u</em> has kinetic energy. When it pierces the block of wood, the block exerts a force of friction on the bullet. As the bullet passes through the block, work is done against the resistive forces exerted on the bullet by the block. This results in the reduction of the bullet's kinetic energy. The bullet has a speed <em>v</em> when it emerges from the block.
If the block exerts a resistive force <em>F</em> on the bullet and the thickness of the block is <em>x</em> then, the work done by the resistive force is given by,
This is equal to the change in the bullet's kinetic energy.
If the thickness of the block is reduced by one-half, the bullet emerges out with a velocity v<em>₁.</em>
Assuming the same resistive forces to act on the bullet,
Divide equation (2) by equation (1) and simplify for v<em>₁.</em>
Thus the speed of the bullet is 71 m/s
Answer:
a) See attached picture, b) We know the initial velocity = 0, initial position=0, time=12.0s, acceleration=, c) the car travels 172.8m in those 12 seconds, d) The car's final velocity is 28.8m/s
Explanation:
a) In order to draw a sketch of the situation, I must include the data I know, the data I would like to know and a drawing of the car including the direction of the movement and its acceleration, just like in the attached picture.
b) From the information given by the problem I know:
initial velocity =0
acceleration =
time = 12.0 s
initial position = 0
c)
unknown:
displacement.
in order to choose the appropriate equation, I must take the knowns and the unknown and look for a formula I can use to solve for the unknown. I know the initial velocity, initial position, time, acceleration and I want to find out the displacement. The formula that contains all this data is the following:
Once I got the equation I need to find the displacement, I can plug the known values in, like this:
after cancelling the pertinent units, I get that my answer will be given in meters. So I get:
which solves to:
So the displacement of the car in 12 seconds is 172.8m, which makes sense taking into account that it will be accelerating for 12 seconds and each second its velocity will increase by 2.4m/s.
d) So, like the previous part of the problem, I know the initial position of the car, the time it travels, the initial velocity and its acceleration. Now I also know what its final position is, so we have more than enough information to find this answer out.
I need to find the final velocity, so I need to use an equation that will use some or all of the known data and the unknown. In order to solve this problem, I can use the following equation:
Next, since I need to find the final velocity, I can solve the equation just for that, I can start by multiplying both sides by t so I get:
and finally I can add to both sides so I get:
and now I can proceed and substitute the known values:
which solves to:
