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GCSE: Forces and Motion

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Balanced and unbalanced forces

  1. 1 There are many words which mean force. E.g. push, pull, friction, weight, air resistance, tension, thrust. All are measured in newtons (N).
  2. 2 When a body is acted on by more than one force at the same time, the overall force is called the resultant force. E.g. if a car is pushed to the right with a force of 500 N and to the left with a force of 200 N, the resultant force is 300 N.
  3. 3 When the resultant force is greater than zero, the forces are unbalanced and this will cause a change in speed or direction, or both. For the example of the car, the 200 N resultant force would cause the car’s speed to increase so the car is accelerating.
  4. 4 What if the brakes are applied to the car? The braking force acts in the opposite way to the direction in which the car is moving. This time the speed decreases and the car is decelerating.
  5. 5 When the resultant force is zero, the forces are balanced. The body will continue to move with a constant speed in the same direction. This is true for a skydiver falling with a constant speed called the terminal speed. The air resistance is equal to the weight.

Acceleration

  1. 1 When the forces on a body are unbalanced, the resultant force, F causes an acceleration, a. We can calculate the acceleration using an equation F = ma.
  2. 2 In this equation m is the mass of the body measured in kilograms (kg). F is the force measured in newtons (N) and a is the acceleration measured in m/s2.
  3. 3 You should practice how to write the equation in three different ways by rearranging it:

    1) F = ma
    2) m = F/a
    3) a = F/m
  4. 4 Suppose a resultant force of 20 N acts on a body giving it an acceleration of 4 m/s2. What is the mass of the body? Choose an equation for m, so we use m=F/a = 20/4 = 5N.
  5. 5 A car of mass 2000 kg is acted on by a force of 500 N. What is the acceleration? Choose the equation for a, so we use a = F/m = 500/2000 = 0.25 m/s2.

Motion under gravity

  1. 1 The weight of a body, W is a force and it can be calculated from the equation W=mg. g is the gravitational field strength. On Earth, g has a value of 9.81 N/kg.
  2. 2 What is the weight of a mass of 20 kg? W = mg = 20 x 9.81 = 196.2 N
  3. 3 On the Moon, the value of g is much smaller than on Earth , so the same body will have a smaller weight . The value of g on the Moon is about one sixth of g on Earth so the weight will be ⅙ of the weight on Earth. So the mass of a body doesn’t change when the body is moved from the Earth to the Moon but its weight changes.
  4. 4 If weight is the only force acting on a body, then we can use the weight to calculate the acceleration when a body is released. What is the acceleration of an apple of mass 0.1 kg which falls from a tree? W = mg = 0.1 x 9.81 = 0.981 N. Now we can calculate the acceleration using a = F/m. (Remember that F=W) so a = 0.981/0.1 = 9.81 m/s2.
  5. 5 Even if we had changed the mass of the apple to 0.2 kg, the acceleration would still be the same! The apples would hit the ground at the same time.

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  1. Coursework Investigation: the Pendulum

    So the pendulum that has to travel the furthest will take the longest amount of time. Aim: To investigate the period of swing of a pendulum. Planning Experimental Procedures: The period of a pendulum is one swing of a pendulum; it is often called an oscillation or a vibration. The complete swing of a pendulum is the swing from left to right and back again. Variables: ? Weight of the bob. ? Air resistance of the bob. ? Length of string. ? Angle of swings. ? Force of the push. ? Size of the gravitational force.

    • Word count: 972
  2. Runny Oils Coursework

    We also found suitable start and finish marks for which the ball could pass through. Also using this method is far more practical, engine designers, for example, have to work out how long a liquid will take to pour down a tube. The diagram below shows how many different paths the oil could take going down a slide, with a tube the U shape at the bottom keeps the ball going in a straight line. This gives us far better results to take speeds of the ball from.

    • Word count: 3152
  3. Acceleration of falling cones Investigation

    On the moon a feather and a golf ball were dropped at the same time, they both hit the surface of the moon at the same time. In any atmosphere when there is a gas or a liquid they initially drop at the same acceleration, encountering a drag force; this increases as it goes faster. The drag force increases until it equals the weight force, the forces are then balanced and it can't go any faster. This is called terminal velocity.

    • Word count: 1242
  4. To find out how increasing the height an object is dropped from, affects its average speed.

    1. Collect equipment (see below) 2. Set up metre stick along table leg 3. Prepare and weigh plasticine balls, making sure they are spherical 4. Hold the ball with the bottom of the plasticine just above measurement 5. Drop the ball timing it with the stopwatch until the exact moment it hits the floor 6. Record results on a table (not the same table as the table leg (!) (Not funny-ed.) Equipment: Stopwatch x2 Plasticine (2 grams) Weighing scales Metre stick Parachute (plastic carrier bag) Fair Test: I will make sure this is a fair test by using the same size, weight and density plasticine each time.

    • Word count: 1166
  5. Vehicle Anti-lock Braking Systems

    Under these circumstances, friction opposes the movement of the vehicle?s wheels along the road. Therefore, friction decreasing when the vehicle begins to slide means less force is opposing the vehicle?s movement to slow it down, increasing the vehicle?s stopping distance[3]. The driver also becomes unable to steer as the wheels do not have enough grip on the road to turn, meaning the driver cannot veer to avoid collision (figure 1). Image result for abs braking ABS allows vehicles to stop faster whilst still maintain control of the car (the wheel?s do not lock)[4]. The driver is still able to steer by using two braking techniques; threshold and cadence braking.

    • Word count: 1599
  6. Engineering Analysis of the Intamin Accelerator Roller Coaster

    On the back of the OTSR there are two hydraulic cylinders each side. As the rider pulls the restraints down, hydraulic fluid is 'sucked' into the cylinders. Once the OTSR are in a safe and comfortable position and they have been checked, the ride operator closes the valves which allow hydraulic fluid to both enter and leave the cylinders. The hydraulic system allows the restraints to be pulled down and locked in any position to better match a rider's body dimensions.

    • Word count: 872
  7. Controlled Assesment Experiment - The extension of a rubber band depends on the force applied.

    Without these fundamental forces, human and all the other matter in the world would fall apart and float away. Example: If you were a tennis ball and someone served you, a force would have acted on you. As a result, you would go bouncing down the court. There are often many forces at work. Let's have a look at the forces acting on that tennis ball before you served it. As it sat there, the force of gravity was keeping it on the ground, while the ground pushed upward, supporting the ball. On a molecular level, the surface of the ball was holding itself together as the gas inside of the ball tried to escape.

    • Word count: 2368
  8. Medical Effects of Roller coasters

    Heart * A roller coaster ride can seriously affect the cardiac health of people with heart conditions. According to this Science Daily, roller coaster loops, plunges and climbs increase the heart rate, resulting in an uneven rhythm that could increase the risk of a cardiac arrest or any other illness. Cardiologists recommend against roller coasters for individuals who have suffered a cardiac arrest have or have heart diseases. Ears * A report by Detroit's Henry Ford Hospital connects roller coaster rides with ear barotraumas.

    • Word count: 547
  9. Determining Gravity with a Pendulum

    L = distance between pivot point and center of the pendulum (m) g = value of acceleration due to gravity (ms-2) In order to determine the acceleration due to gravity, the equation were to be arranged to g = Equipment * Scissors * Pendulum (approx 300g) * Whiteboard Diagram Hanger * Whiteboard * Texture * Whiteboard Texture Holder * Sticky Tape * 2m String * Stop Watch Method 1. Set up the pivot point location on the whiteboard as shown in the diagram 1.1 in appendix 1 by using the sticky tape to tape the whiteboard diagram hanger onto the magnetic whiteboard marker holder.

    • Word count: 1836
  10. Physics Pendulum Practical. How does the time period vary with length and what is the value of g?

    Time taken for 20 oscillations 2. Value of g (supposed to be constant variable) Manipulation of Variables Controlled or Constant Variables: 1. Bob: We used the same bob for all trials so that all the results acquired are relevant to one bob only. 2. Mass of bob: Since we used the same bob for all trials, the mass of the bob did not change and remained constant for all trials. 3. String used: We used the same string in all trials to maintain accuracy of the data. 4. Amplitude of oscillation: We made sure that in each trial, the initial amplitude of the oscillation remained approximately 15°.

    • Word count: 1189
  11. Report on Newton's laws of motion

    Newton?s main fields were science and mathematics. He created the well-known famous calculus before Leibniz' became popular. On the other hand, Newton's most affective and famous discovery was gravity which states that {the earth's (gravitational pull) pulls objects toward it}. Newton came up with three laws of motion; these laws form the base of the first branch of physics (Classical Mechanics). What is unique about Newton?s laws is that they explain the way objects move and this is done by finding the relationship between force and motion on the macroscopic level. These laws are the reason behind making physics applicable almost all over the universe except for quantum mechanics, the second branch of physics, which focuses more on the motion at a microscopic level.

    • Word count: 1891
  12. Designing an Efficient Balloon Car

    These different pieces of the car working together help it perform well. For the thrust of our car, we used a balloon attached to a PVC pipe. This pipe allowed us to let the air out of the balloon more quickly. It also helped us to direct the air straight back from the balloon. The more air we were able to release, the more negative horizontal acceleration we could have. However much acceleration there is in the negative is how much there will be in the positive because of Newton?s Third Law of Motion. The more air that is released in the negative will push the car forward faster.

    • Word count: 616
  13. Need For Speed: High Speed Trains

    So engineers were needed to devise a train that could travel at very fast speeds while keeping energy consumption as low as possible. The Japanese started the race for faster high speed trains with their ?bullet trains?, the French countered with the TGV, and many other companies came out with their own high speed trains: Acela, Eurostar, and the Shinkansen, among others [3]. The increase in competition benefitted the consumer, the individual needing to get across the continent because now he or she had a choice between different trains, each known for a specific accommodation.

    • Word count: 1310
  14. Rocket Essay. How Do Rockets Work?

    work on studying the air quality, alternative energy, climate changes, and near earth objects, so whenever there?s a typhoon, earthquake, or any other natural disaster, we could known before hand so we can prevent it or reduce the amount of damage done. How Do Rockets Work? The simplest form of a rocket is a chamber enclosing a gas under pressure. A small opening at one end of the chamber which allows the gas to escape, so that the pressure provides a thrust that propels in the opposite direction, and these pressures are hat pushes the rocket along.

    • Word count: 1094
  15. What are the laws of Physics involved in the design of the roller coaster?

    Centripetal Acceleration ? The formula for centripetal acceleration is ? ar = v^2 / r where ar ? acceleration, v ? velocity and r ? radius. This acceleration is caused by the centripetal force which act towards the centre of the loop. 1. 'G' ? forces ? Greater the centripetal acceleration, greater the 'g' forces which represent the gravitational pull on the riders. 1G is the usual force of gravity felt on Earth. When you feel weightless you experience 0G.

    • Word count: 1064
  16. Experiment To Investigate What Affects the Size of a Crater

    Adjust it until the edges of the caliper touches the surface of the sand. Read the measurement and record it down. Results are tabulated. 1. Controlled: Height of the sand, Volume of the sand, diameter of the pendulum ball Height of sand is measured with the same ruler used in the experiment and marked out with a marker. The volume of same is measured by pouring it into a beaker and then weighed on an electronic weighing balance for further accuracy. The diameter of the pendulum ball was measured before the start of the experiment and noted down.

    • Word count: 872
  17. How does length affect the time period of the pendulum?

    And the movement of the pendulum would be due to the gravitational force. Variables:- Independent Dependent Constant Length of the string Time period Mass of bob Manipulation of variables:- Independent:- Length- As the length increases the time period increases too, and as the length decreases the time period also decreases Dependent:- Time period- Is affected by the change in length, and is directly proportional to length Constant:- Mass of bob- is kept constant as the factor taken is the length Apparatus:- 1. String 2. Bob 3. Stop watch 4. Pendulum stand 5. Rubber split corks to hold string Method:- 1.

    • Word count: 605
  18. Sources of Energy in the World

    But where does energy come from? Sources of Energy We get our energy from many sources on this planet. These sources can be mainly divided into two categories: Sources of Energy Nonrenewable Energy Renewable Energy Renewable Energy Renewable energy is energy which comes from sources that can be replenished. These sources never die out and there is no pollution when you use them. The most common renewable sources are: 1. Wind Energy: The energy in the wind is harnessed when the wind currents turns the turbine in the windmill. 1. Solar energy: The energy from the sunlight is harnessed through solar cells.

    • Word count: 1244

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