Kinematics
A machine is a device that accepts energy in some available form and utilizes it to do a type of work. Energy, work, or power has to be transferred from one mechanical part to another to run a machine. While the transfer of energy between two machine parts, those two parts experience a relative motion with each other. Studying such relative motions is termed kinematics.
Kinetic Energy and Work-Energy Theorem
In physics, work is the product of the net force in direction of the displacement and the magnitude of this displacement or it can also be defined as the energy transfer of an object when it is moved for a distance due to the forces acting on it in the direction of displacement and perpendicular to the displacement which is called the normal force. Energy is the capacity of any object doing work. The SI unit of work is joule and energy is Joule. This principle follows the second law of Newton's law of motion where the net force causes the acceleration of an object. The force of gravity which is downward force and the normal force acting on an object which is perpendicular to the object are equal in magnitude but opposite to the direction, so while determining the net force, these two components cancel out. The net force is the horizontal component of the force and in our explanation, we consider everything as frictionless surface since friction should also be calculated while called the work-energy component of the object. The two most basics of energy classification are potential energy and kinetic energy. There are various kinds of kinetic energy like chemical, mechanical, thermal, nuclear, electrical, radiant energy, and so on. The work is done when there is a change in energy and it mainly depends on the application of force and movement of the object. Let us say how much work is needed to lift a 5kg ball 5m high. Work is mathematically represented as Force ×Displacement. So it will be 5kg times the gravitational constant on earth and the distance moved by the object. Wnet=Fnet times Displacement.
- What is the equation for horizontal work?
- Rogelio pushes a book 3 m across the table. If he uses a force of 10N, what is the work done?
- In a physics equation, what does Δ mean?
- ΔKE= ___________KE - ____________KE
- Ms. Thomas was falling down a hill. If her KE at the top of the hill was 56J and halfway down was 85 J, what was her ΔKE?
- ΔKE= ½ m______ - ½ m_______
- Eric throws a 6 kg ball with a velocity of 25 m/s. If the velocity just before it hit the ground was 54 m/s, what was the ΔKE?
- Write, in your own words, the Work-Energy Theorem.
Part Two: Practice Problems
- A 2200 kg car accelerates from 25 m/s to 65 m/s. How much work does the car generate?
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Step 1: Givens/Unknowns |
Step 2: Left Side -Circle the correct W Fd |
Step 3: Right Side -Circle the correct ΔKE KEf-KEi 1/2mvf2-1/2mvi2 |
Step 4: Solve |
- A ball is kicked 30m. If the final KE is 3000N, with what force was the ball kicked?
|
Step 1: Givens/Unknowns |
Step 2: Left Side -Circle the correct W Fd |
Step 3: Right Side -Circle the correct ΔKE KEf-KEi 1/2mvf2-1/2mvi2 |
Step 4: Solve |
- A 50 kg football player gets pushed with a force of 25N. If he accelerates from 30 m/s to 55 m/s, how far was he pushed?
|
Step 1: Givens/Unknowns |
Step 2: Left Side W Fd |
Step 3: Right Side ΔKE KEf-KEi 1/2mvf2-1/2mvi2 |
Step 4: Solve |
- Ms. Thomas is riding her scooter across campus. If the combined mass is 35 kg and she speeds up from 10 m/s to 25 m/s, how much work did it take to accelerate?
- What is the ΔKE if a grocery cart is pushed 12 m with a force of 15N?
- If a 25 kg bike is pushed from rest with a force of 15 N moving at 12 m/s, how far did it travel?
- If 30,000 J of work is done on a 2400 kg box that started from rest, what is the final velocity of the box?
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