Forces, velocities and angles

In summary, the conversation is about a take home quiz for physics class and the person has answered 7 out of 10 questions. They need help with the remaining questions and are looking for assistance in setting up the problems and using formulas to solve them. The hardest question is #3 which involves calculating the values of C and T using two simultaneous equations or the law of sines. Question #2 involves calculating the speed of a rocket after all its fuel has been exhausted. Question #5 involves finding the angle between a string and the vertical axis in a car moving at a constant speed around a curve. The person also mentions that the test is open book and open notes and seeking help is allowed. They express their confusion about the purpose of the
  • #1
:::JMANN:::
21
0
I have a take home quiz for my physics class. Out of the 10 questions I have answered 7 of them, whether they are right I don't know. First and foremost I need help on the ones I haven't solved yet. I am not necessarily looking for someone to give me the answers, but rather help me setup the problem and use formulas to arrive at the answer myself.

The hardest question is #3.

A 200lb man stands tiptoed on one foot so that all his weight is borne by the ground beneath the ball of the foot. If the foot and ankle are considered as an isolated body, the three forces that are in equilibrium are the reaction W of the ground, the pull T of the achillies tendon and the compression C of the tibia. The force C is downward at an angle 15* from vertical. The force T is upward at 21* from the vertical. W is an upward force of 200lbs. Calculate the values of C and T. (HInt: one way to do this is to have two simultaneous equations, one balancing the horizontal components of force and the other balancing the vertical components. Another way is to use the law of sines)

#2.

A rocket exhausts fule with a velocity of 1500m/s, relative to the rocket. It starts from rest in outer space with the fuel comprising 80% of the total mass. When all the fuel has been exhausted, what is the rockets speed?

#5.

A car rounds a 75m radius curve at a constant speed of 18m/s. A ball is suspended by a string from the ceiling of the car and moves with the car. What is the angle between the string and the vertical (y-axis)?
 
Physics news on Phys.org
  • #2
If this is a take home TEST, are you allowed to seek help from others? If that is true then I see no point in the test at all.
 
  • #3
Yes, it is open book open notes. We are allowed to seek help too. He wants us to understand the concepts and apply them, even if we are aided, rather than stay confused and not know what we are doing.
 
  • #4
well for problem three he basically tells you how to do it: it's a vector math problem. You want to take the x and y components of the C and T vectors and set them equal to the W (normal) force

something like:
C cos(theta1) + T cos(theta2) = 0
C sin(theta1) + T sin(theta2) = 200lbs
 

Related to Forces, velocities and angles

What is the difference between force and velocity?

Force is a measure of the push or pull on an object, while velocity is a measure of the speed and direction of an object's movement.

How does an object's angle affect its velocity?

The angle of an object's movement will determine its direction and therefore, its velocity. A change in angle can result in a change in velocity, either increasing or decreasing its speed and/or changing its direction.

What is the relationship between force and acceleration?

Newton's Second Law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This means that the greater the force applied to an object, the greater its acceleration will be.

How do forces affect an object's motion?

Forces can cause an object to change its velocity, either by speeding it up, slowing it down, or changing its direction. These changes in motion are a result of the net force acting on the object.

What is the difference between static and kinetic friction?

Static friction is the force that prevents an object from moving when a force is applied to it, such as pushing a book on a table. Kinetic friction is the force that occurs when an object is in motion and is being slowed down by a surface, such as a car braking on a road.

Similar threads

  • Introductory Physics Homework Help
Replies
7
Views
640
  • Introductory Physics Homework Help
Replies
3
Views
988
  • Introductory Physics Homework Help
Replies
2
Views
330
  • Advanced Physics Homework Help
Replies
7
Views
3K
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
3K
  • Introductory Physics Homework Help
Replies
15
Views
5K
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
17
Views
2K
Back
Top