Work-kinetic energy theorem

In summary, the conversation discusses how to calculate the average force due to air resistance on a chunk of ice falling from the CN tower. The tower is 553m tall and the ice has a mass of 25.0g and a speed of 33.0m/s as it passes a restaurant located 353m above the ground. The conversation mentions using the concept of work and change in kinetic energy to solve the problem, and suggests calculating the work done by air resistance by finding the difference between the kinetic energy without air resistance and with air resistance.
  • #1
elitespart
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The CN tower in 553m tall. Suppose a chuck of ice w/ a mass of 25.0g falls from the top of the tower. The speed of the ice is 33.0m/s as it passes the restaurant in the tower located 353m above the ground. What is the average force due to air resistance?

I'm having trouble getting started on this problem. I know how to calculate work and change in KE, but how do I use those to get the answer? Any help would be appreciated.
 
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  • #2
elitespart said:
The CN tower in 553m tall. Suppose a chuck of ice w/ a mass of 25.0g falls from the top of the tower. The speed of the ice is 33.0m/s as it passes the restaurant in the tower located 353m above the ground. What is the average force due to air resistance?

I'm having trouble getting started on this problem. I know how to calculate work and change in KE, but how do I use those to get the answer? Any help would be appreciated.

You could start by figuring out what the ice's velocity would be without any air resistance.
 
  • #3
ok now what
 
  • #4
He's implying to look at the loss in kinetic energy...

Now, how would you calculate the work done by air resistance?
 
  • #5
find diff. b/w KE w/out air resistance and with air resistance?
 
Last edited:

1. What is the work-kinetic energy theorem?

The work-kinetic energy theorem is a fundamental principle in physics that states that the net work done on an object is equal to the change in its kinetic energy. In other words, when a force is applied to an object, it will either accelerate or decelerate, and the work done by that force will be equal to the change in the object's kinetic energy.

2. How is the work-kinetic energy theorem derived?

The work-kinetic energy theorem is derived from the laws of motion and the concept of work. It can be mathematically proven by using the equations for work and kinetic energy and manipulating them to show that they are equal. Alternatively, it can also be derived from the principle of conservation of energy.

3. What are the units for work and kinetic energy?

The units for work are joules (J), which is equal to 1 newton-meter (N·m). The units for kinetic energy are also joules (J), since it is a form of energy. However, in some cases, kinetic energy may be expressed in other units such as electron volts (eV) or foot-pounds (ft·lb).

4. Can the work-kinetic energy theorem be applied to all types of motion?

Yes, the work-kinetic energy theorem can be applied to all types of motion, including linear, rotational, and even vibrational. As long as there is a force acting on an object and it experiences a change in velocity, the theorem can be used to calculate the work done on the object and its resulting change in kinetic energy.

5. Is the work-kinetic energy theorem a conservative or non-conservative principle?

The work-kinetic energy theorem is a conservative principle. This means that the work done by conservative forces, such as gravity or electrostatic forces, can be easily calculated using the theorem. On the other hand, for non-conservative forces, such as friction or air resistance, the work-kinetic energy theorem cannot be directly applied and additional calculations must be made.

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