How does height influence velocity.

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Daniel Rollé

Physics Coursework

How does height influence velocity

Rationale: When an object is at the top of a slope its position above the ground provides it with gravitational potential energy. As it moves down the slope, the object loses potential energy but as energy cannot be destroyed, it is converted into kinetic energy. Assuming that the system is 100% efficient all of the potential energy will be converted into kinetic energy at the bottom of the slope. We can use this information to predict the speed at which the object should move when it reaches the bottom of the slope.

Aim: To investigate how the velocity of an object changes when the height of the ramp it moves down is changed.

Introduction: Energy cannot be created or destroyed, it exists in many forms all around us, and we cannot sense it or feel it- it is just there. Potential energy, gravitational potential energy, elastic energy, chemical energy, nuclear energy, kinetic energy, thermal energy, electrical energy and radiant energy are examples of them.

Friction is one the most important forces that we use in everyday life. Without it we would not be able to walk or even move about. Cars would not work and you would not be able to write.  Before the time of Galileo and Newton, people thought there was only one force, called a driving force. Newton discovered that there were unseen forces like friction and air resistance all around us, helping us do everything.

Therefore, when you push a car down a ramp, the forces acting on it are friction, driving force and air resistance. These are unbalanced forces as the car is moving forward meaning the driving force is greater than the air resistance and friction. As the car moves down the ramp it converts potential energy, as it is stationary on the top of the ramp, into kinetic energy as it comes down the ramp. The formula for finding out the strength of a force is Force = Mass x Acceleration. The force is measured in Newtons (N), the mass is measured in kilograms (Kg) and the acceleration is measured in metres per second per second (M/s/s). To work out the kinetic energy is Kinetic Energy = 0.5 x mass x (Velocity x velocity) or ½mv². Kinetic energy, like potential energy, is measured in joules. Kinetic energy is moving energy.  The formula used to find out gravitational potential energy is Gravitational potential energy = mass x gravitational field strength x height or mgh. The height is measured in metres.  Gravitational potential energy is stored energy that can be turned into kinetic energy.

The Formula which we will use in the experiment is V =     2GH  

This shows the speed or velocity will equal the square root of two times gravity times height. The gravity is measured in N/Kg and gravity on earth is 10 N/Kg.  Here is an example of how to calculate   2GH:

If the height was 5 cm the equation is:

2 x 9.8(the gravitational pull) x 0.05m= 0.98 m/s  

Friction is the force that slows down moving objects. The size of the friction force depends on the roughness of the surfaces: the rougher the surfaces, the greater the friction force. Air resistance is the force that slows down falling objects. When an object is moving forward the main resistive force is air resistance. Gravity is the force that keeps objects on the ground.

Speed is determined using the formula, Speed = Distance

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Distance and time can also be shown on a Distance-Time graph. If you go on a journey, the distance you have travelled can only stay the same or increase, so a Distance-time graph for the same journey cannot have a negative gradient. The graph below shows this:

Speed is ...

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