Calculate Max Speed of Truck on Unbanked Curve Without Eggs Sliding

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Homework Help Overview

The discussion revolves around two distinct physics problems: one involving the motion of a probe launched from the Moon and another concerning the maximum speed of a truck negotiating an unbanked curve without causing a crate of eggs to slide. The first problem relates to circular motion and gravitational acceleration, while the second focuses on static friction and centripetal acceleration in a vehicle dynamics context.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants explore the relationship between speed, radius, and gravitational forces in circular motion. There are attempts to apply formulas for centripetal acceleration and static friction, with some questioning the correctness of their calculations and assumptions.

Discussion Status

Several participants have provided insights into the equations governing circular motion and static friction. There is an ongoing exploration of how to derive necessary values, such as normal force and maximum static friction, while others are clarifying their understanding of the relationships between variables involved in the problems.

Contextual Notes

Participants are navigating through the complexities of circular motion, including the implications of using static friction in the context of the truck problem. There are mentions of specific values, such as the radius of the curve and the coefficient of static friction, which are critical to the discussions but may not be fully resolved.

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Homework Statement


An astronaut on the surface of the Moon fires a cannon to launch an experiment package, which leaves the barrel moving horizontally. Assume that the free-fall acceleration on the Moon is one-sixth that on the Earth. Radius of moon = 1.74 * 10^6 m
a) What must be the muzzle speed of the probe so that it travels completely around the Moon and returns to its original location? Found out to be 1.68km/s
b) How long does this trip around the Moon take?

Homework Equations


a=\omega^2r

v=\omega r

The Attempt at a Solution


I tired to solve with constant acceleration formulas.
a=1.62m/s^2
vi=0
vf=1.68km/s => 1678.928m/s

vf=vi+at
16878.928=0+1.62t
t=10419.09136s

2)A crate of eggs is located in the middle of the flat bed of a pickup truck as the truck negotiates an unbanked curve in the road. The curve may be regarded as an arc of a circle of radius 35.0m. If the coefficient of static friction between crate and truck is 0.600, how fast can the truck be moving without the crate sliding?

I have tried to do the following:

i know the static friction: 0.600

i need to know \omega

which is \sqrt{9.8}{35}, \omega=0.529

find velocity

v=r\omega
v=0.529 * 35
v=18.52m/s

i know this is incorrect, someone tell me how i can approach this.
 
Last edited:
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Paymemoney said:

Homework Statement


An astronaut on the surface of the Moon fires a cannon to launch an experiment package, which leaves the barrel moving horizontally. Assume that the free-fall acceleration on the Moon is one-sixth that on the Earth. Radius of moon = 1.74 * 10^6 m
a) What must be the muzzle speed of the probe so that it travels completely around the Moon and returns to its original location? Found out to be 1.68km/s
b) How long does this trip around the Moon take?


Homework Equations


a=\omega^2r

v=\omega r

The Attempt at a Solution


I tired to solve with constant acceleration formulas.
a=1.62m/s^2
vi=0
vf=1.68km/s => 1678.928m/s

vf=vi+at
16878.928=0+1.62t
t=10419.09136s
This is a circular motion/orbit problem. Use Newton's 2nd law and the formula for centripetal acceleration.
 
how can i find the time with the centripetal acceleration formula?
 
Paymemoney said:
how can i find the time with the centripetal acceleration formula?
OK. Looks like you solved for the speed (but didn't show your work). The speed is constant. What distance does it travel in going around once?
 
do you mean \omega = 9.649 * 10^{4} rad/s?
 
Paymemoney said:
do you mean \omega = 9.649 * 10^{4} rad/s?
You could certainly use that if you like. But that should be 10-4!

I was thinking of distance = speed * time. You have the speed. And you should be able to calculate the distance, then solve for the time.
 
How can i find the distance if i only have velocity, acceleration?
 
Paymemoney said:
How can i find the distance if i only have velocity, acceleration?
What path does it take? Hint: Make use of the moon's radius.
 
would you find the diameter of the moon, which is 3480000?
 
  • #10
Answer this: What is the shape of the package's orbit around the moon?
 
  • #11
well the shape of a car...
 
  • #12
Paymemoney said:
well the shape of a car...
:bugeye:

It goes all the way around the moon in a big circle!
 
  • #13
i misunderstood your question. -_-
 
  • #14
Do you understand what I mean now? How can you find the length of that path? (Remember that this is a question about circular motion.)

(You could also solve for the time using ω, which you've already calculated.)
 
  • #15
yes, i understand it took me awhile -_-.

So from the equation: \omega = \frac{\theta}{t}

derived from the linear v=\frac{x}{t}

where:

\theta = 2\pi because it go around once.

\omega = 9.649 * 10^{-4}t=\frac{2\pi}{9.649*10^{-4}}

t=6511.74765s

t=\frac{6511.74765}{3600} turn into hours

t=1.81hrs however book's answer has a slight difference in 1.80hrs. Edit** i know why because of my rounding off.
 
  • #16
would someone answer my second question?
 
Last edited:
  • #17
Paymemoney said:
yes, i understand it took me awhile -_-.

So from the equation: \omega = \frac{\theta}{t}

derived from the linear v=\frac{x}{t}
You used the first equation, but you could also have used the second one directly. When it goes around once, the package traces the circumference of a circle. So x = 2\pi r.
 
  • #18
Paymemoney said:
2)A crate of eggs is located in the middle of the flat bed of a pickup truck as the truck negotiates an unbanked curve in the road. The curve may be regarded as an arc of a circle of radius 35.0m. If the coefficient of static friction between crate and truck is 0.600, how fast can the truck be moving without the crate sliding?

I have tried to do the following:

i know the static friction: 0.600

i need to know \omega

which is \sqrt{9.8}{35}, \omega=0.529

find velocity

v=r\omega
v=0.529 * 35
v=18.52m/s

i know this is incorrect, someone tell me how i can approach this.
How did you solve for ω?

Again, this is a circular motion problem that can be solved using Newton's 2nd law and what you know about centripetal acceleration.

What force acts on the eggs? What's the expression for its acceleration?

FYI: ac = ω²r = v²/r
 
  • #19
Doc Al said:
How did you solve for ω?

Again, this is a circular motion problem that can be solved using Newton's 2nd law and what you know about centripetal acceleration.

What force acts on the eggs? What's the expression for its acceleration?

FYI: ac = ω²r = v²/r

the mass and the centripetal force.

Don't i need to use the static friction?
 
  • #20
Paymemoney said:
Don't i need to use the static friction?
Yes. Static friction is the only force available to provide the centripetal acceleration.
 
  • #21
So would i start by finding the fsmax by using the equation

coefficient of static friction = \frac{fsmax}{n}
 
  • #22
Paymemoney said:
So would i start by finding the fsmax by using the equation

coefficient of static friction = \frac{fsmax}{n}
Right. The static friction will be at its maximum, so F = μN. (What's N?)

Now apply Newton's 2nd law.
 
  • #23
the normal
 
  • #24
how do i find the N?
 
  • #25
Paymemoney said:
how do i find the N?
To find an expression for the normal force, analyze the vertical force components. What's the net vertical force?
 
  • #26
would it be F=N -mg
 
  • #27
Paymemoney said:
would it be F=N -mg
Right. And what must F equal in this case?
 
  • #28
the static friction force
 
  • #29
Paymemoney said:
the static friction force
No. We're talking about vertical forces here. What's the net vertical force? (Is there any vertical acceleration?)

The purpose is just so you can find the normal force.
 
  • #30
wouldn't that be mg?
 

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