Centripetal force question + other question

In summary, the conversation is discussing problems related to circular motion and vertical motion of objects. The first problem involves finding the mass of a dog sitting on a merry-go-round, given its angular speed and the force keeping it in circular motion. The second problem involves calculating the vertical displacement of an olympic runner during a hurdle jump, with an initial vertical speed given. The conversation also includes tips for solving the problems, such as re-writing equations and identifying relevant information.
  • #1
demode
30
0
1. A dog sits 1.50 meters from the center of a merry-go-round with an angular speed of 1.20 rad/s. If the magnitude of the force that maintains the dog's circular motion is 40.0 N, what is the dog's mass?



2. Fc = (mv^2) / r



3. We were provided with the answer "18.5" but I do NOT understand how you can get this value using the aforementioned equation. I'll demonstrate what I did:
40 * 1.50 = (1.20^2)m
60 = 1.44m
m = 41.6 kg
can someone explain to me what I'm doing wrong?



1. An olympic runner leaps over a hurdle. If the runner's initial vertical speed is 2.2 m/s, how much will the runner's center of mass be raised during the jump?



2. NO IDEA



3. Don't even know WHERE to begin. Can someone help me out?
 
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  • #2
To start off, I'd assume that for the speed, you mean 1.20 m/s, right?

For your first problem, I'll suggest rewriting the equation. Re-write it to solve for what you're looking for. Then, try it again, and see what you come up with.

For the second problem, think about what you would need to know to solve the problem, then write them down. This could get you to think of how you could actually solve the problem.
 
  • #3
It appears you were given an angular speed of 1.2rad/s. This is NOT the same as linear speed. You must find the equation that relates angular speed to linear speed (v), then plug in that value of v into your correct equation to solve for m.

In part 2, you need to know either the motion equation that relates velocity, acceleration, and displacement, OR the conservation of energy theorem that relates kinetic and potential energies. Are you familiar with either of these equations?
 

Related to Centripetal force question + other question

1. What is centripetal force?

Centripetal force is the force that acts on an object to keep it moving in a circular path. It is always directed towards the center of the circle.

2. How is centripetal force calculated?

Centripetal force can be calculated using the formula Fc = mv^2 / r, where Fc is the centripetal force, m is the mass of the object, v is the velocity, and r is the radius of the circular path.

3. What is the difference between centripetal force and centrifugal force?

Centrifugal force is often confused with centripetal force, but they are actually two different forces. Centripetal force is the inward force that keeps an object moving in a circular path, while centrifugal force is the outward force that is experienced in a rotating reference frame.

4. What are some real-life examples of centripetal force?

Some real-life examples of centripetal force include a ball being swung around on a string, a car turning around a curve, and the Earth revolving around the sun.

5. How does centripetal force relate to Newton's laws of motion?

Centripetal force is related to Newton's first law of motion, also known as the law of inertia, which states that an object in motion will stay in motion unless acted upon by an external force. In this case, the centripetal force is the external force that is acting on the object to keep it moving in a circular path.

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