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GCSE: Forces and Motion
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Balanced and unbalanced forces
- 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 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 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 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 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.
- 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 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.
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 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 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 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 What is the weight of a mass of 20 kg? W = mg = 20 x 9.81 = 196.2 N
- 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 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 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.
This means that the golf ball is possibly going to be the one that bounces the highest and the most efficient, the tennis ball will bounce the second highest and the second most efficient, and the field hockey ball will bounce the third highest and the least efficient. Materials: * * golf ball * tennis ball * field hockey ball * a flat surface * 2 meter sticks * tape * electronic balance Procedures: 1. Mass each of the spheres using the electronic balance and record the mass 2.
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This is in scale with the ramp in a way that matches a car going down a road. I also tried different balls to make sure that the marble would give me the most reliable results.
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and a hollow rubber ball (squash ball)), plastic and wood (a hollow wooden ball) Hypothesis: Based upon prior experience with the squash ball and the crazy ball only, a hypothesis can be stated that the crazy ball is likely to bounce the most, while the squash ball is likely to bounce the least. The squash ball actually begins to bounce only after heating up during a game and merely dropping it several times is not enough to heat it up. Thus as a fair test, its bounce at room temperature will only be investigated.
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Preliminary Work During my preliminary work I tested the lowest and highest heights from which I , I did this to find the shortest and longest times it would take to do the experiment. The results obtained are shown below: Distance from which released (cm) Height from which released (cm) Time 1 (s)
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In this experiment we are focusing on a particular type of potential energy, gravitational energy. (From here on, the phase potential energy will be referred to as gravitational potential energy.) Potential energy is the energy stored in an object as a result of its vertical position (i.e., height.) The energy is stored as the result of the gravitational attraction of the earth for the object. There is a direct relationship between the potential energy, the mass of the object and also the height of the object. In this case we are using the same trolley so therefore the mass is the same, but we are changing the gradient of the ramp and by changing the gradient we are also changing the height.
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They work by applying the crash's stopping force to more durable parts of the body over a longer period of time. For instance, if your car were to crash into a telephone pole at 50 mph, your speed is obviously independent to that of the car. The force of the pole would bring the car to an abrupt stop, but your speed would remain the same.
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The direction associated with the disturbance is at right angles to the direction of travel by the transverse wave. The disturbance is in the same direction as that of the longitudinal wave. The pulses of this two type of waves can be sent along a slinky spring. In this experiment, both the transverse and longitudinal pulses are generated bt\y the hand, and the speed of the transvers pulses along the spring c can be found by: c = whereT is the tension of the spring and �is the mass per unit length of the spring. Procedure 1. A long spring was stretched on the floor over a distance of about 10m.
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The mass of the rubber bung and the screw nuts was weighed with a balance. 4. The glass tube was held vertically and the rubber bung was whirled around in a horizontal circle, the paper mark should be just below the glass tube. 5. The time for 50 revolution was recorded using a stop watch. 6. Step 1-5 should be repeated with different length of string. Precaution: 1. The paper mark should not be in contact with the glass tube when whirling the rubber bung, i.e. there was no friction between the glass tube and the rubber bung. 2.
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It is energy needed to raise the temperature of a material or substance by 1oC, in other words, 1K. Method: 1. Choose a metal block from copper, brass, aluminum and steel, and set up the rest of the experiment as shown in the diagram.
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When the elastic band is pulled back, tension in the band causes potential energy and when you let go, the potential energy is transferred to kinetic energy in the band, thus creating movement. One of the forces that affect the tub from continuously moving is friction. Friction works in opposition with the movement of the object. The surface of the tub is rough and the surface of the floor is also rough, so the two surfaces catch and the tub slows down.
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Solution : Velocity on striking the ground, V=V(2gh) =V(2105) =10m/sec Velocity of rebounding V�=V(2gh�) =V(2101.25) =5m/sec Change in momentum =mv- (-mv�) =mv+mv� =m(v+v�) =((20010��) (10+5)) =(0.215) =3kgm/sec Force time = 3kgm/sec F 0.2 sec= 3kg/sec So F = F= 15N 3) A cricket ball of mass 150g moving with a speed 12m/s is hit by bat so that the ball is turned back with a velocity 20m/sec.
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In the graph you can see that the two sets or results i have collect are very similar meaning there are less gap for mistakes, while looking at the results i can predict that the higher the volume the higher the pressure. The results Evaluation In conclusion I think that the pressure and temperature did have change throughout the test, the pressure was keeping the same pattern all the way through, to make the test more reliable I would have to repeat the test several times.
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The length of the thread was noted. 5. We had then moved the thread with the bob between 5 to 10 . 6. The thread was then allowed to do few oscillations before we started the stopwatch. 7. After 3-4 oscillations, we started the stopwatch and counted 20 oscillations. 8. As soon as the 20 oscillations were completed, we stopped the stopwatch and recorded its time taken.
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between the successive dots equals the average speed of the object * 1/5 s is called a tentick * 5 tenticks = 1 second 7. Photogate timer * They are used to record time taken for a trolley to pass through a gate. If the length of the interrupt card is measured, the velocity can be calculated Graphs and equations 8. Velocity - time graphs o Tape charts are velocity - time graphs which show the velocity changing in jums rather than smoothly.
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Evaluation: * A parallax error may have taken place; eyes must be directly above the reading of the thermometer. * Stirring could have generated a little extra heat, which may have altered results. Measuring Objects using the Metre Rule and Vernier Calliper Aim: To find the level of accuracy and the more accurate measuring instrument between the metre rule and the vernier calliper, by measuring the diameter of an object. Apparatus: * Vernier calliper * Metre rule * Object (cube)
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Physics - how the launch height affects the horizontal distance a ski jumper travels from the launch ramp
Shown in diagram (1) bellow. To make measuring more accurate we used a setsquare to make sure that we knew we were measuring from exactly the right point. Shown in diagram (2) bellow. We measured the horizontal distance from the closest point to the table; we measured the value to the nearest 'mm', each time to make our results consistent. Sand Type: In our experiment the ball would run off the ramp and land in the tray of sand and we measured the horizontal distance travelled by the ball was measured by the crater in the sand.
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Because the simple pendulum moves in the arc of a circle, as the displacement will be an angular displacement rather than the linear displacement we have been using so far. The two forces on the bob are its weight (mg) and the tension is T in the string. The component of the weight along the direction of the string, the component of the weight at right angles to the direction of the string mg and sin are the restring force.
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The air resistance involved in this experiment does not affect the marble as much as the gravity involved but can still limit the amount of speed the marble can gain which puts a limit on the height of which the marble can be dropped from in order to achieve accurate results. Preliminary Test: I chose top do a preliminary test in order to familiarise myself with the experiment and the method of using the equipment involved. I also chose to do this because if I found a way of carrying out the experiment using a better technique to gather more
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This is because the weight is great than the drag force, causing there to be an unbalanced force. The force necessary to accelerate an object by a given amount depends on the object's mass, therefore the greater the mass, the greater the force must be. Chosen Variable I have decided choosing the total surface area of the wingspan in my investigation and the reasoning behind this decision is that I believe this variable from my preliminary work would be much better to collect results from for my analysis. When executing my preliminary tests prior to this investigation, I noticed that when dropping my helicopter with an altered mass, the vertical acceleration time did not seem to have considerable differences between the starting and finishing points as it did for the wingspan.
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n my experiment I will be heating and cooling a double yellow squash ball to see if it changes the bounce of the squash ball in any way.
It was a brand new double yellow squash ball. I also had to keep the floor on which I dropped it on to the same, luckily for me all the science labs have the same floor so there was no problem with the surface of the floors. Method First of all I decided to choose a suitable height to drop the squash ball from, I chose a height of 1.00 meter because the benches in the labs are exactly that height and It would also be a good place to set up the motion sensor.
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Also the experiment would not be a fair test. Fair Test The height that the ball bounces after being released from a recorded height will be measured. The ball will only be dropped on a selected surface and this surface will not be changed. If the surface was different for every individual test the ball would bounce to different heights and the experiment therefore would be unfair. The ball will be dropped rather than thrown to ensure that the experiment is as fair as possible. If the ball was thrown the force on the ball would be more than wanted and the ball would collide with the surface much sooner than required.
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It has a heavy base in comparison to the model's body, and has a large base area. * Principle Two: Stability One of the key properties of the okiagari-koboshi is that it does not topple or fall down no matter how one pushes it. The okiagari-koboshi would rock back up to its original state and position. To fulfill this requirement, the object has to remain at a stable equilibrium at all times, regardless if it is being pushed. To keep the model at a stable equilibrium, the centre of gravity must be as low as possible and the base area as large as possible, so as to keep the model at its maximum stability.
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An ordinary shelf has similarities to a bridge. As a further example, structural form of Thames bridges in London was considered. In all cases structures need to be specially designed to respond to different loading conditions that can occur.
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The symbol for torque is ?, the Greek letter tau. The principle of moments is: f (1) x d (1) = f (2) x d (2) Apparatus: * Retort Stand  * Meter Rule  * Newton metre  * String  Illustration: Variables: Independent: Distance between the pivot and the metre rule Dependent: Weight (Force of the metre rule on the Newton metre) Constant: Apparatus, environment [temperature etc.]. Method/Procedure: * Clamp the metre rule to one of the retort stands at the 1cm mark. * Tie a loop on either sides of a string. * Put one loop through the metre rule and the other loop to the Newton metre.
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My first controlled variable is the amount of extension I put on the spring before letting it go and timing it. I had decided on a fixed extension I would use on all experiments but after my preliminary experiments were carried out I found out that the amount of extension put on the spring did not affect the time it took for completing 30 oscillations. I controlled the amount of extension because I thought that it would affect the time it takes for a number of oscillations.
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