Select all that apply. The force that opposes the start of motion is referred to as _____. starting friction
sliding friction
static friction
kinetic friction


Answer 1
Answer: The correct answers are starting friction and static friction

Friction slows down all forces, but starting friction slows down or stops completely the start of motion.

Answer 2

Answer: Option (c) is the correct answer.


A force helps to keep an object at rest is known as static friction. This type of friction avoids the movement of object from its initial place unless and until a larger force than the friction force is applied on the object.

Whereas sliding friction is the friction that is experienced when object is sliding. On the other hand, kinetic friction is the friction experienced when an object is moving from it initial place.

Thus, we can conclude that out of the given options the force that opposes the start of motion is referred to as static friction.

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HELP ASAP A roller coaster is 1/2 way down, what form of energy does this roller coaster have at this point?



It has both kinetic and potential

At an amusement park, a Physics 114 takes a ride on a fast-moving Ferris wheel. The apparent weight of the student is different at the top than at the bottom. What is the ratio of the student’s apparent weight at the top to the student’s apparent weight at the bottom, given that the radius of the loop-the-loop is 27.0 m and the student completes three revolutions every 150 seconds? The mass of the student is 55 kg.



N1 / N2 = 1.0016


The apparent weight of the student is the value that a balance would have this corresponds in this case to the normal of the student. Let's write Newton's second law in the lower and upper part of the loop

For lower rotating wheel

    N1 - W = m a

    a = v² / r

    N1 = W + v² / r

The relationship between linear and angular velocity is

    v = w r

As the wheel rotates at a constant speed, we can use angular kinematics

    w = θ / t

    θ = 3 rev (2π rad / 1rev) = 6π rad

    w = 6π / 150

    w = 0.04π rad / s = 0.1257 rad / sec


   N1 = mg + w² r

   N1 = 55 9.8 + 0.1257² 27

   N1 = 539 + 0.4267

   N1 = 539.426 N

Now we perform the same calculation for the top

   -N2 - W = -m a

    N2 = -W + ma

    N2 = 539 - 0.4267

    N2 = 538.5733 N

The relationship between the weight at the bottom and top is

   N1 / N2 = 539.4267 / 538.5733

   N1 / N2 = 1.0016


What is the mass of an object that weighs 686N on Earth?



70 kg




m= 686/9,8= 70kg


1.a bag is dropped from a hovering helicopter. the bag has fallen for 2 s. what is the ball's velocity at the instant its hitting the ground? what was the height of the helicopter? if the bag was dropped from a helicopter descending at the speed of 2 m/s what is the time of the bag fall and its velocity near the ground?


1. The bag's velocity immediately before hitting the ground.

Recall this kinematics equation:

Vf = Vi + aΔt

Vf is the final velocity, Vi is the initial velocity, a is the acceleration, and Δt is the time elapsed.

Given values:

Vi = 0m/s (you assume this because the bag is dropped, so it falls starting from rest)

a is 9.81m/s² (this is the near-constant acceleration of objects near the surface of the earth)

Δt = 2s

Plug in the values and solve for Vf:

Vf = 0 + 9.81×2

Vf = 19.62m/s

2. The height of the helicopter.

Recall this other kinematics equation:

d = ViΔt + 0.5aΔt²

d is the distance traveled by the object, Vi is the initial velocity, a is the acceleration, and Δt is the time elapsed.

Given values:

Vi = 0m/s (bag is dropped starting from rest)

a = 9.81m/s² (acceleration due to gravity of the earth)

Δt = 2s

Plug in the values and solve for d:

d = 0×2 + 0.5×9.81×2²

d = 19.62m

3. Time of the bag's fall and its velocity immediately before hitting the ground... if it started falling at 2m/s

Reuse the equation from question 2:

d = ViΔt + 0.5aΔt²

Given values:

d = 19.6m (height of the helicopter obtained from question 2)

Vi = 2m/s

a = 9.81m/s² (acceleration due to earth's gravity)

Plug in the values and solve for Δt:

19.6 = 2Δt + 0.5×9.81Δt²

4.91Δt² + 2Δt - 19.6 = 0

Use the quadratic formula to get values of Δt (a quick Google search will give you the formula and how to use it to solve for unknown values):

Δt = 1.8s, Δt = −2.2s

The formula gives us 2 possible answers for Δt but within the situation of our problem, only the positive value makes sense. Reject the negative value.

Δt = 1.8s

Now we can use this new value of Δt to get the velocity before hitting the ground:

Vf = Vi + aΔt

Given values:

Vi = 2m/s

a = 9.81m/s²

Δt = 1.8s (result from previous question)

Plug in the values and solve for Vf:

Vf = 2 + 9.81×1.8

Vf = 19.66m/s


HELP ME PLEASE In which prenatal stage is a fetus' genitalia clearly male or female?
A. zygote stage B. germinal stage C. embryonic stage D. fetal stage


In the fetal stage, the genitalia of a fetus is developed. Thus option D, the fetal stage is correct.

What is the prenatal stage?

The time period from the formation of the zygote to the parturition is called the prenatal stage and it is also known as the antenatal stage. In this stage, division and differentiation of the zygote take place to form an embryo, and then the development of the embryo to form a fetus.

The prenatal stage consists of 3 stages:

1) Germinal stage

2) Embryonic stage

3) Fetal stage

The time period of the first two weeks after conception is known as the germinal stage, from the third to eighth week is the embryonic stage, this stage begins after implantation, and from the ninth week to the parturition is the fetal stage. The genitalia of a fetus can be clearly differentiated by the twelfth week.

Therefore, option D, the fetal stage is correct.

Learn more about the prenatal stage, here:



D is the right answer



The platform height for Olympic divers is 10 m. A 60 kg diver steps off the platform to begin his dive. a. How much gravitational potential energy does the diver have?

b. How much kinetic energy does the diver have as he strikes the water?

c. How much work does the water do on the diver to stop his momentum?

d. If the diver stops in 2.5 m after entering the water, what net force is applied to the diver?


The gravitational potential energy of the diver is 6000 J.

The gravitational potential energy = mgh

m = mass of the diver = 60 kg

g = acceleration due to gravity = 10 ms-2

h = height =  10 m

gravitational potential energy = 60 kg ×  10 ms-2 × 10 m = 6000 J

Recall that the potential energy of the diver = kinetic energy does the diver have as he strikes the water. Hence, kinetic energy does the diver have as he strikes the water is 6000J.

The work done by the water= gravitational potential energy.

Hence, the  work done by the water on the diver to stop his momentum = 6000 J.

Recall that; work done = Force × distance

Force = work done/distance

Force = 6000J/2.5 m

Force = 2400 N

Learn more:


a) Ep = 5886[J]; b) v = 14[m/s]; c)   W = 5886[J]; d) F = 1763.4[N]



The potential energy can be found using the following expression, we will take the ground level as the reference point where the potential energy is equal to zero.


Since energy is conserved, that is, potential energy is transformed into kinetic energy, the moment the harpsichord touches water, all potential energy is transformed into kinetic energy.


The work is equal to

W = 5886 [J]


We need to use the following equation and find the deceleration of the diver at the moment when he stops his velocity is zero.

By performing a sum of forces equal to the product of mass by acceleration (newton's second law), we can find the force that acts to reduce the speed of the diver to zero.

m*g - F = m*a

F = m*a - m*g

F = (60*39.2) - (60*9.81)

F = 1763.4 [N]


every computer consists of physical components and non physical components the non physical component of a computer that understand how to work with the physical components are referred to as_________



C. software


software, is a collection of data or computer instructions that tell the computer how to work. This is in contrast to physical hardware, from which the system is built and actually performs the work.





I have a question... it's pretty tough... maybe you can help me? _____________________

#19 The thing wire in the previous question will convert electromagnetic force into______.

A. Voltage
B. Amperes
C. Current
D. All of the above
E. None of the above


You are probably thinking... 'what is the previous question?!'
I'm one step ahead of you ;-)



#20 A thick wire will have ___(less)___ resistance than a thin wire of the same material.

A. Open
B. Marginal
C. Greater
D. Less
E. None of the above



So I was wondering if you could help me on #19...
I'm not great at science...



I think the answer is CURRENT...
Number 19: Is A let me know if you need help with number 20


What potential difference is needed to give a helium nucleus (q=2e) 85.0 kev of kinetic energy?


The kinetic energy K given to the helium nucleus is equal to its potential energy, which is 

where q=2e is the charge of the helium nucleus, and  is the potential difference applied to it.
Since we know the kinetic energy, we have

and from this we can find the potential difference:

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