Willing to pay 15fg per answers, i know its not much but it is still something! Please explain how you get the answers so then i will know how to do them.

Item #1:
In this problem, you will apply kinematic equations to a jumping flea. Take the magnitude of free-fall acceleration to be 9.80m/s2 . Ignore air resistance.

Part A:
A flea jumps straight up to a maximum height of 0.360m . What is its initial velocity v0 as it leaves the ground?
Express your answer in meters per second to three significant figures.

Item #2:
Learning Goal:
To clarify the distinction between speed and velocity, and to review qualitatively one-dimensional kinematics.
A woman stands at the edge of a cliff, holding one ball in each hand. At time t0, she throws one ball straight up with speed v0 and the other straight down, also with speed v0.
For the following questions neglect air resistance. Pay particular attention to whether the answer involves "absolute" quantities that have only magnitude (e.g., speed) or quantities that can have either sign (e.g., velocity). Take upward to be the positive direction.

Part A:
If the ball that is thrown downward has an acceleration of magnitude a at the instant of its release (i.e., when there is no longer any force on the ball due to the woman's hand), what is the relationship between a and g, the magnitude of the acceleration of gravity?


a>g
a=g
a<g

Part B:
Which ball has the greater acceleration at the instant of release?


the ball thrown upward
the ball thrown downward
Neither; the accelerations of both balls are the same.

Part C:
Which ball has the greater speed at the instant of release?


the ball thrown upward
the ball thrown downward
Neither; the speeds are the same.

Part D:
Which ball has the greater average speed during the 1-s interval after release (assuming neither hits the ground during that time)?


the ball thrown upward
the ball thrown downward
Neither; the average speeds of both balls are the same.


Part E:
Which ball hits the ground with greater speed?


the ball thrown upward
the ball thrown downward
Neither; the balls hit the ground with the same speed.

Item #3
A student drops a ball from the top of a tall building; the ball takes 2.4s to reach the ground.

Part A:
What was the ball’s speed just before hitting the ground?
Express your answer using two significant figures.

Part B:
What is the height of the building?
Express your answer using two significant figures.

Item #4
A test rocket containing a probe to determine the composition of the upper atmosphere is fired vertically upward from an initial position at ground level. During the time t while its fuel lasts, the rocket ascends with a constant upward acceleration of magnitude 2g. Assume that the rocket travels to a small enough height that the Earth’s gravitational force can be considered constant.

Part A:
What are the speed and height, in terms of g and t, when the rocket’s fuel runs out?
Express your answer in terms of g and t. V=


Part B:
Express your answer in terms of g and t. H=

Part C:
What is the maximum height the rocket reaches in terms of g and t?
Express your answer in terms of g and t. Hmax=

Part D:
If t = 34.0s , calculate the rocket’s maximum height. Hmax=

Item #5
Unless otherwise stated, all objects are located near the Earth's surface, where g = 9.80 m/s2 .
A force acts on a 2.0kg , mass, giving it an acceleration of 3.0m/s2 .

Part A:
If the same force acts on a 2.9kg mass, what acceleration would be produced?
Express your answer using two significant figures. a=

Part B:
What is the magnitude of the force?
Express your answer using two significant figures. F=



Item #6
Unless otherwise stated, all objects are located near the Earth's surface, where g = 9.80 m/s2 .
A gun is fired and a 46g bullet is accelerated to a muzzle speed of 120m/s .

Part A:
If the length of the gun barrel is 0.70m , what is the magnitude of the accelerating force? (Assume the acceleration to be constant.)
Express your answer using two significant figures.

This post was edited by Stolem on Nov 4 2013 11:31pm

For many of these problems, utilize the parabolic motion equation:

x(t) = 1/2*g*t^2 + v_0*t + h

where g is the gravitational constant, v_0 is your initial speed, and h is your initial height.

Also use v_f^2 - v_i^2 = 2*g*(x-x_0)

where v_f is the final velocity, v_i is the initial velocity, g is the gravitational constant, x is the final position, and x_0 is the initial position.

For example, for the first problem,

Because you know the acceleration (-9.8), we can use the second equation.

v_f, in this case, is zero because we want to find the initial velocity it takes to reach the top of the parabolic motion (which by definition requires zero vertical motion at the peak).

v_i is the variable we want to solve for. g is 9.8, x_0 is zero because we can choose any coordinate for the zero, and it makes sense to use where the flea jumped from. Therefore, v_i^2 = 2*(9.8 m/s^2)(0.360m). solve for v_i.

Item #3
A student drops a ball from the top of a tall building; the ball takes 2.4s to reach the ground.

Part A:
What was the ball’s speed just before hitting the ground?
Express your answer using two significant figures.

Part B:
What is the height of the building?
Express your answer using two significant figures.

For part B, I'm lazy to do the equation and looking it up
But isnt the equation something like d = Vit - 2at^2
or something close to that
You got your Vi, you dropped it so its 0
a = -9.8 and time is 2.4

Item #2:
Learning Goal:
To clarify the distinction between speed and velocity, and to review qualitatively one-dimensional kinematics.
A woman stands at the edge of a cliff, holding one ball in each hand. At time t0, she throws one ball straight up with speed v0 and the other straight down, also with speed v0.
For the following questions neglect air resistance. Pay particular attention to whether the answer involves "absolute" quantities that have only magnitude (e.g., speed) or quantities that can have either sign (e.g., velocity). Take upward to be the positive direction.

Part A:
If the ball that is thrown downward has an acceleration of magnitude a at the instant of its release (i.e., when there is no longer any force on the ball due to the woman's hand), what is the relationship between a and g, the magnitude of the acceleration of gravity?

a=g


Part B:
Which ball has the greater acceleration at the instant of release?

Neither; the accelerations of both balls are the same.

Part C:
Which ball has the greater speed at the instant of release?

Neither; the speeds are the same.

Part D:
Which ball has the greater average speed during the 1-s interval after release (assuming neither hits the ground during that time)?

the ball thrown downward



Part E:
Which ball hits the ground with greater speed?

Neither; the balls hit the ground with the same speed.

This post was edited by Azrad on Nov 5 2013 12:49am

For more explanation. MAGIC

Lol, I already pm'd him all of items 1-6 with explanations, he's offline though.

In all of the problems, I'm using the variables a=acceleration, v=final velocity, v(0)=Initial Velocity, t=time, and x=displacement.

1A )For the first problem, it is pretty simple kinematics. We know that a=9.8m/s^2, x=.36m, and since it is rising and then stopping, the final velocity must be zero. So we know these variables:
a=9.8m/s^2
x=.36m
v=0m/s
We're solving for initial velocity and don't know the time so we use the equation v^2=v(0)^2+2ax.
Plus in the values to get 0=v(0)^2+2(9.8m/s^2)(.36) and solve that for a final answer of v(0)=2.66m/s.

2A) a=g This is because there are no other forces acting, so gravity provides the only acceleration for both balls. The acceleration and gravity are working in opposite directions, but their magnitude is equal.
2B) Equal. Again, this is because gravity is the only force acting on the balls.
2C) The speed of the balls is equal because as said in the problem, she propels each ball with an equal v(0). At the instant of release, neither ball has acceleration or decelerated at all.
2D) The ball going downward. It's faster because it is accelerated downwards in that one second, while the acceleration in the upward ball decreases its speed since it acts downwards.
2E) The ball thrown upward. This is because it rises until it is not moving, then from this greater distance it falls and accelerates downward for a longer time than the ball that started downwards could accelerate. I can explain this further if you don't understand.

3A) This is very similar to problem A. Let's go over the variables we know.
The ball is dropped from rest, so v(0)=0m/s
Acceleration in these problems is the same, a=9.8m/s^2
And time is given, t=2.4s.
We're solving for final velocity and don't know displacement, so I'll use the equation v=v(0)+at
Plugging in our values we get v=(-9.8m/s^2)(2.4s) for a final answer of v=23.52m/s.

3B) Again the same variables from above apply, but now we're solving for displacement so I'll use the equation x=(v+v(0))(t/2).
This gives us an answer of x=28.224m.

5A) First of all, we need to know that F=ma. If you understand this very simple equation then the following problems will be quite easy.
To start off, we will plug in the given 2kg mass with a 3m/s^2 acceleration to find that the force is 6N.
Then we can just use 6N with the 2.9 kg mass to find the acceleration. a=(6N/2.9kg). a=2.07m/s^2.
5B) And...we've already found the magnitude of the force as part of A, F=6.0N.

6B) This problem we'll split into two parts. In the first, we'll use kinematics to find the acceleration, and in the second we'll use our calculated acceleration to find the magnitude F.
We know the bullet starts from rest, and we know it travels a distance of .7m, with its final velocity being 120m/s. This gives us the variables:
x=.7m
v=120m/s
v(0)=0m/s
Now we can use kinematics as we did in the first three items, this time using the equation v^2=v(0)^2+2ax to find the acceleration.
Plug in the values to get (120m/s)^2=(2)(.7m)a, and solve for a to find that a=10,286m/s^2. This number might seem ridiculous at first, but consider that in a distance of less than 1 meter the bullet accelerates to a speed of 120m/s, and it suddenly becomes much more reasonable.
Now that we know A, we just need to use F=ma with the given mass. However, remember to convert the mass into kg because they are the standard unit and your answer will be incorrect otherwise.
F=(10,286m/s)(.046kg)
F=473.16N.

This post was edited by weslee on Nov 5 2013 12:39am

Part E:
Which ball hits the ground with greater speed?
By symmetry when the ball thrown upwards falls and reaches the height at which it was released, it will have the same position, velocity and acceleration as the ball that was thrown downward at its release point. In other words, they will share the same initial conditions, so they will have the same results when you apply the kinematic equations.

This post was edited by Azrad on Nov 5 2013 01:05am

Thank you...this was the only question I wasn't entirely sure about. I thought it would work this way but I asked a friend who's gone through quite a bit more physics than me and he said they would land at the same speed, lol.