Forces and Problem Solving

Forces Definition: A force is a push, pull or a twist that results in an object changing its shape of or motion. Types of forces: 1) Friction – is a force which acts against the force of motion. 2) Air Resistance – is the force acting against an object moving through the air. A type of friction. 3) Motion – is the force of movement. 4) Gravitation – is the force of attraction toward the centre of an object that has mass. 5) Magnetic – is the force of attraction of substance containing iron (Fe) because of the magnetic field. 6) Electric – is the force of attraction or repulsion due to the type of charge (+/-) in an object. Measuring a Force: Forces are usually measured in newtons after the scientist who made the first significant discoveries. 1 newton is equal to 100 grams weight under earths gravity.

The Uses of Steam Anything that requires mechanical power can use steam to drive its motion. Steam was the original source of power for transport and industry. However as early as 300BC the steam turbine was invented. If it was not for the fall of the Greek and Roman empire then the industrial revolution may have occurred 2000 years earlier.

Investigation – Steam Turbine Aim: To build a working model of a steam turbine and describe the three forces involved in its operation. Method:1) Set up the apparatus as shown in the diagram below. 2) Suspend the turbine from a retort stand and clamp by tying it with string. 3) Heat the water inside the test tube with a Bunsen burner and stand about 1 metre back to observe it work. Results: Draw a scientific diagram of the apparatus labelling the forces and motions you observed. Conclusion: Explain how the steam turbine created the forces you identified. Bunsen burner Test tube Water Retort stand and clamps String Top view Bent pin Glass tube Cork

Investigation - Magnets Aim: To observe the patterns of magnetic forces created by magnets. Method: 1) Collect two bar magnets, a sheet of paper and some iron filings. 2) Place the bar magnets in the arrangements as shown in the below diagrams but do not allow them to connect. 3) Put a sheet of plain paper over the magnets and then sprinkle iron filings over the sheet. 4) Observe the patterns created by the force fields. Results: Draw scientific diagrams of the various patterns you observe. Conclusion: Explain the significance of the various patterns. N S

Magnets Magnets have a strange power of attraction and repulsion. This is because of the invisible force field around them. Invisible it may be and yet very real because we can witness their effect on both same and different poles as well as iron filings. We see their pattern as lines of force so we know that they exist even though we cannot see them on their own. These lines of force can be bent and distorted by the interaction with other lines of force so that we can explain our observations.

Investigation – Electric Force Aim: To show that electric charges create a force using a Van de Graff generator. Hypothesis: Write an if…then statement identifying the variable and prediction. Method:1) Set up the apparatus as shown in the picture to the right. Turn on the Van de Graff with the grounding rod and step back. 2) Bring the rod close to the dome of the Van de Graff. Holding it off to one side give the best results. Slowly move the rod around to see the little lightening bolts. 3) Once you have finished with the demonstration, turn off the Van de Graff with the grounding rod, and touch the rod to the machine afterwards in order to extract any charge remaining there.

Results: Discussion:1) Identify the evidence for a force being involved in your observations. 2) Define the term force. 3) Explain how electric charges create a force. Conclusion: Was the hypothesis supported or rejected? Why? Describe the force created by an electric charge.

Van de Graff Generator

Galileo Studies Motion In the time of the Greek Empire, philosophers argued about the speed of a falling object. Aristotle, in 350B.C. believed that an object fell with the same speed throughout its fall. By the early 1600’s most intellectual people still believed that objects fall with a constant speed. However Galileo was known for going against popular beliefs and in fact he was under house arrest for doing just that, sentenced for heresy (believing ideas that went against the teachings of the church) . While he was confined to his home he began to study motion. Galileo designed an experiment to test this idea. He hypothesized that the metal ball would travel faster as the height was increased.

Experiment – Acceleration of Falling Objects. Aim: To measure the speed of a falling object at different heights. Hypothesis: If an object is dropped from a greater height then its speed will also be greater. Method:1) Set up the apparatus as shown below. 2) Set the ramp to an initial height and record this height. 3) Discuss with your prac team the variables that will need to be controlled to make this experiment a fair test. Record these controls in the discussion section of this experiment. 4) Roll the marble down the ramp and record the time it takes to travel a known distance from the bottom of the track. 5) Calculate the final speed using the equation below. 6) Repeat steps 4 and 5 doubling the height then again increasing the height by the same amount. 3rd height 2nd height Initial height Ramp Marble Start timing Finish timing Known distance Retort stand Speed = Distance / Time

Results: Speed Ramp height Discussion:1) Identify the dependent, independent and controlled variables. 2) Assess the reliability of your results by comparing with the other prac groups. Conclusion: Was your hypothesis supported or rejected? Why? Were the results agreeing with Aristotle or Galileo? Remember that all graphs need a heading, appropriate scales, units for each scale, plotting with X’s, the graph line must take up approximately 80% of the axis space and has a key if more than one line is used.

Gravity In 1687 Isaac Newton was sitting under an apple tree when one apple fell on his head. This caused for him to wonder about the forces that made this happen. Newton reasoned that there is a force between the earth and all other objects which pulls them together. This became his theory of gravitation. This theory had further applications such as astronomy where the planets were kept in their orbital motions by the force of gravity and it was realised that the object with the greater mass had the greater gravitational force and the sun was certainly big enough. No longer was it believed that gods pushed the planets around in space which is why astrology used the stars to predict the future. Newton’s theory was able to explain how planets moved in space and proved Kepler’s theory of planetary motion which had been based on observations. The two theories became a Natural Law of Science. Newton had brought the whole universe under one set of natural laws based on the principle of universal gravitation. Newton’s law had a major influence on scientific thinking up to the present day.

Investigation – Measuring the force of Gravity Aim: To measure the force of gravity using Newton’s Laws of Gravity. Hypothesis: If gravitational force equals mass X acceleration then the force of gravity can be calculated. Method:1) Weigh a ball accurately with electronic scales and record its mass. 2) Measure the distance for the ball to fall under the force of gravity. 3) Drop the ball and measure the time it takes to complete the total distance and the set distance at the end of the fall. Record both distances and times. 4) Repeat this 5 times and calculate an average for these times. 5) Use the formulas below to calculate V2, then A and finally F. F=MXA A=V2-V1 t V2=d/t Starting position Total distance and time End position Set distance and time for V2 Path of falling ball

Results: Calculations: Complete your calculations as described in step 5. Discussion:1) Assess the accuracy of your results by comparing them with the accepted acceleration value of 9.8m/s. 2) Assess the validity of the experiment by determining if the hypothesis and aim are answered. 3) Propose ways to improve the accuracy of your results and identify the problems that need to be solved if you cannot suggest any. 4) Identify the dependent, independent and controlled variables. 5) Outline the significance of Newtons theory of gravity. Conclusion: Was your hypothesis supported or rejected? What would you need to do to improve the accuracy of this experiment.

Galileo V’s Aristotle In the late 1500's, everyone knew that heavy objects fall faster than lighter ones. After all, Aristotle had said so back in 300BC. The fact that an ancient Greek scholar still held such influence1800 years in the future is a sign of how far science had declined during the dark ages. Galileo was cheeky enough to question this common understanding. The story has become part of the folklore of science: he is reputed to have dropped two different weights from the town's Leaning Tower of Pisa in 1604 showing that they landed at the same time. His challenges to Aristotle may have cost Galileo his job at Pisa University, but he had demonstrated the importance of taking scientific investigation and not human authority, as the final determination in the truth of nature.

Investigation – Gravity, Mass & Falling Aim: To test the falling speed of two same sized objects with different masses. Hypothesis: Write an if…then statement identifying the variable and prediction. Method:1) Collect two objects of the same size and shape. This is to eliminate wind resistance as another variable so that a fair test is performed. 2) These objects have a different weight. Using the electronic scales weigh and record the mass of the two objects. 3) From the same elevated position drop the objects at the same time. 4) With observers looking at ground level, watch to see which object hits the ground first. Record your observations. Results:

Discussion: 1) Identify the dependent, independent and controlled variables. 2) Assess the validity of the two theories proposed by Aristotle and Galileo. 3) Outline how the reliability of the results can be improved for this investigation. Conclusion: Was your hypothesis supported or rejected? Why? Explain the effect of mass on a falling object. Galileo hypothesised that in a vacuum, with no air resistance, the effect of mass on a falling object would not change its speed in fall. During the moon mission of Apollo 15 in 1971, the third last visit to the moon and first use of the Luna buggy, astronaut Dave Scott performed an experiment for Galileo. In the last moments of the time spent on the lunar surface he pulled out a geologists hammer and a falcon feather. He dropped them at the same time and the result was…… (see “From the Earth to the Moon Part 10”)

Galileo’s Experiment

Pendulum While Galileo was attending church at the Cathedral, he noticed that the chandeliers were swinging in the wind and he used his pulse to time its movement. He discovered something unusual and came up with a conclusion. This conclusion led Galileo to suggest that swinging pendulums could be used to measure time. Galileo’s idea was the basis of the first mechanical clocks.

Assessment task - Pendulum Definitions for the parts of an experiment report; Aim: The purpose of the investigation or the question to answer. Hypothesis: An If….then statement with the variable identified and a prediction included. Results: Record of your measurements and relevant observations organised in a table where possible. Discussion: An assessment of the significance and trends of the results. An assessment of the reliability of the results and the validity of the experiment. Improvements to the procedure to increase accuracy. Reliability: same results, repeated, agrees with referenced results or follows a clear trend. Validity: is the hypothesis investigated, is the aim answered? Conclusion: Is the hypothesis supported or rejected? Provide an answer for the aim referring to the trend in the results only. Do not quote the results again. Describe an application for your conclusion to science or society. This assessment task will be included in your total assessment mark as well as assessing the specific outcomes for your report. You have TWO weeks to complete this task but you can get a ONE week extension with a note from your parents explaining why you could not complete the task in the given time before the due date. Organise your materials and arrange adult supervision

Sir Isaac Newton Newton was a way cool science dude No it was mine It was my idea Come on It was my great, great grandapple

Research Task - Newton In this task you are to research the life, time and work completed by Sir Isaac Newton. The information that must be included is; 1) Date and place of birth and death. 2) A picture of him to show what he looked like. 3) Identifies his schooling, career and personality. 4) Outlines the work he did in studying motion and gravity. 5) Assesses the implications of his work on science and society. 6) Description of the time and world Newton worked in. NO EXCUSES OK!!! You must answer these questions directly and using only your words. You have 2 weeks to complete this task and your report should be neatly presented on A4 paper to earn top marks. Write it in your planner

Sir Isaac Newton Einstein 1) Newton, Sir Isaac (1642-1727), mathematician and physicist, one of the foremost scientific intellects of all time. Born at Woolsthorpe, near Grantham in Lincolnshire, Newton died at Kensington on 20March 1727 and was buried in Westminster Abbey on 28 March. 2) He attended school, he entered Cambridge University in 1661; he was elected a Fellow of Trinity College in 1667, and Lucasian Professor of Mathematics in 1669. He remained at the university, lecturing in most years, until 1696. 3) Of these Cambridge years, in which Newton was at the height of his creative power, he singled out 1665-1666 (spent largely in Lincolnshire because of plague in Cambridge) as "the prime of my age for invention". During two to three years of intense mental effort he prepared Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy) commonly known as the Principia, although this was not published until 1687. 4) Newton has been regarded for almost 300 years as the founding examplar of modern physical science, his achievements in experimental investigation being as innovative as those in mathematical research. With equal, if not greater, energy and originality he also plunged into chemistry, the early history of Western civilization, and theology; among his special studies was an investigation of the form and dimensions, as described in the Bible, of Solomon's Temple in Jerusalem. 5) Newton, but was named after him because of his great achievements in the fields of mathematics, optics, physics and astronomy. The Newton Institute continues in this tradition of crossing the boundaries between scientific disciplines. Specific answers to each question written in your own words Example Answer Appropriate Diagrams of Newton Each answer is separate Your name so the teacher knows who to give the marks to Appropriate heading