Exampro GCSE Physics. P3 - Moments, Centre of Mass, Hydraulics and Circular Motion Self study Qs. Name: Class: Author: Date: Time: PDF

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Exampro GCSE Physics P3 - Moments, Centre of Mass, Hydraulics and Circular Motion Self study Qs Name: Class: Author: Date: Time: 28 Marks: 28 Comments: Page of 48 Q. The diagram shows a spanner being used
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Exampro GCSE Physics P3 - Moments, Centre of Mass, Hydraulics and Circular Motion Self study Qs Name: Class: Author: Date: Time: 28 Marks: 28 Comments: Page of 48 Q. The diagram shows a spanner being used to undo a tight nut. The nut was tightened using a moment of 20 newton metres. Use the following equation to calculate the force needed to undo the nut. Show clearly how you work out your answer. moment = force perpendicular distance from pivot Force =... N (Total 2 marks) Page 2 of 48 Q2. The London Eye is the largest observation wheel in the world. The passengers ride in capsules. Each capsule moves in a circular path and accelerates. (a) Explain how the wheel can move at a steady speed and the capsules accelerate at the same time (b) In which direction does each capsule accelerate?... () (c) What is the name of the resultant force that causes the capsules to accelerate?... () Page 3 of 48 (d) The designers of the London Eye had to consider three factors which affect the resultant force described in part (c). Two factors that increase the resultant force are an increase in the speed of rotation an increase in the total mass of the wheel, the capsules and the passengers. Name the other factor that affects the resultant force and state what effect it has on the resultant force () (Total 5 marks) Q3. Tractors are often used on sloping fields, so stability is important in their design. On the diagram, the centre of the X marks the centre of mass of the tractor. (a) Explain why the tractor has not toppled over. You may add to the diagram to help you to explain (3) Page 4 of 48 (b) Give two features of the tractor which affect its stability and state how each feature could be changed to increase the tractor s stability. Feature Feature (Total 5 marks) Q4. (a) The diagram shows a child s mobile. The mobile hangs from point P on the ceiling of the child s bedroom. (i) Mark the position of the centre of mass of the mobile by drawing a letter X on the diagram. Do this so that the centre of the X marks the centre of mass of the mobile. () (ii) Explain why you have chosen this position for your letter X Page 5 of 48 (b) The diagram shows a device which helps to prevent a ladder from falling over. Use the term centre of mass to explain why the ladder, in the situation shown, is unlikely to topple over. You may add to the diagram to illustrate your explanation (3) (Total 6 marks) Page 6 of 48 Q5. This page is from a science magazine. The Red Planet The two natural satellites, or moons, of Mars are Phobos (fear) and Deimos (terror). They are named after the horses which pulled the chariot of Mars, the god of war in the mythology of Ancient Greece. Phobos takes less than eight hours to orbit Mars and gets slightly closer every time it does so. Scientists predict that in about 00 million years time it will either be ripped apart by the gravitational force or will crash onto the surface of Mars. (a) Suggest how scientists have arrived at their prediction of about 00 million years (b) The centripetal force on Phobos is gradually changing as it orbits Mars. Is the force increasing or decreasing?... Explain your answer Page 7 of 48 (c) Scientists expect that the mass of Mars and the mass of Phobos will not increase. Explain what will happen to the gravitational force on Phobos as it orbits Mars (Total 6 marks) Q6. A student wants to weigh himself but the only balance available is a newtonmeter that measures up to 200 newtons. The diagram shows how the student solved the problem using moments. Page 8 of 48 (a) Use the information in the diagram to calculate the weight of the student given by this method. Write down the equation you use, and then show clearly how you work out your answer and give the unit. Weight =... (5) (c) Even though all the measurements are accurate the student s weight obtained by this method is inaccurate. Explain why. (Total 7 marks) Page 9 of 48 Q7. Tractors are often used on sloping fields, so stability is important in their design. On the diagram, the centre of the X marks the centre of mass of the tractor. (a) What is meant by the term centre of mass? () (b) Explain how the design of the tractor could be changed in order to increase the tractor s stability. (c) Explain why the tractor does not topple over. You may add to the diagram to help your explanation. (3) (Total 6 marks) Page 0 of 48 Q8. The fairground ride called The Rotor is a large cylinder which rotates. When the cylinder reaches its maximum speed the floor drops away and the riders inside the cylinder are left against the cylinder wall. (a) Explain how the cylinder is rotating at a constant speed but at the same time the riders inside the cylinder are accelerating. (3) (b) In which direction do the riders accelerate? () (c) What name is given to the resultant force that causes the riders to accelerate? () (d) At the end of the ride the floor goes back into place and the cylinder slows down and stops. How does the resultant force on the riders change as the cylinder slows down? () (Total 6 marks) Page of 48 Q9. The diagram shows a design for a crane. The crane is controlled by a computer. The purpose of the motors and gears is to change the pulling force in the steel cable. This is done so that the jib stays horizontal whatever the size of the load or the position of the load. Use the equation in the box to answer questions (a) and b). moment = force perpendicular distance from the line of action of the force to the axis of rotation (a) Calculate the moment caused by the load in the position shown in the diagram. Show clearly how you work out your answer and give the unit. Moment =... (3) Page 2 of 48 (b) Calculate the pulling force that is needed in the steel cable to keep the jib horizontal. Show clearly how you work out your answer. Pulling force =... N (Total 5 marks) Q0. The diagrams show two concrete mixers. Concrete mixer A Concrete mixer B On each diagram, the centre of the white X marks the centre of mass of the concrete mixer and its contents. (a) Complete the sentence to explain what the term centre of mass means. The centre of mass of a concrete mixer and its contents is... () Page 3 of 48 (b) Both diagrams are drawn to the same scale. Concrete mixer B is more stable than concrete mixer A. The two features which make concrete mixer B more stable are: (c) Use the terms line of action of the weight and resultant moment to explain why a stable concrete mixer does not fall over when it is given a small push. (Total 5 marks) Page 4 of 48 Q. The diagram shows a back view of a computer monitor. (a) In normal use, the monitor is stable. (i) Explain the meaning, in the above sentence, of the word stable. (ii) State the relationship between the total clockwise moment and the total anticlockwise moment about any axis of the monitor when it is stable. () Page 5 of 48 (b) The instruction booklet explains that the screen can be tilted. It also includes a warning. Caution The monitor can tip over if the screen is tilted too far back. Explain why the monitor will tip over if the screen is tilted too far back. Include the words centre of mass, weight and moment in your explanation. (3) (Total 6 marks) Page 6 of 48 Q2. The diagram shows a fork-lift truck with a load of 2.4 kn. The clockwise moment caused by this load is 2880 Nm. (a) Use the equation in the box to calculate the distance d. moment = force perpendicular distance from the line of action of the force to the axis of rotation Show clearly how you work out the answer and give the unit. Distance d =... (3) Page 7 of 48 (b) This warning notice is in the driver s cab. Explain in terms of moments why the maximum load must not be exceeded. (Total 5 marks) Q3. The diagram shows a device called a current balance. (a) (i) When the switch is closed, the part of the wire labelled XY moves upwards. Explain why. Page 8 of 48 (ii) What is the name of the effect that causes the wire XY to move? () (iii) An alternating current (a.c.) is a current which reverses direction. How many times the current reverses direction in one second depends on the frequency of the alternating supply. Describe the effect on the wire XY if the battery is replaced by an a.c. supply having a frequency of 5 hertz. (b) The diagram shows how a small weight can be used to make the wire XY balance horizontally. Use the data in the diagram and the equation in the box to calculate the force, F, acting on the wire XY. moment = force perpendicular distance from the line of action of the force to the axis of rotation Show clearly how you work out your answer. Force =... N (3) (Total 8 marks) Page 9 of 48 Q4. The diagram shows a father and his two children sitting on a playground see-saw. The see-saw is not moving. (a) What is the total clockwise moment of the two children about the axis of rotation? Explain the reason for your answer. (3) (b) (i) What is the clockwise moment of the boy, B, about the axis of rotation? Moment =... Nm () Page 20 of 48 (ii) Use the information in the diagram and the equation in the box to calculate the weight, W, of the boy, B. moment = force perpendicular distance from the line of action of the force to the axis of rotation Show clearly how you work out your answer. Weight of boy B =... N (Total 6 marks) Q5. The London Eye is one of the largest observation wheels in the world. Angelo Ferraris/Shutterstock The passengers ride in capsules. Each capsule moves in a circular path and accelerates. (a) Explain how the wheel can move at a steady speed and the capsules accelerate at the same time. Page 2 of 48 (b) In which direction is the resultant force on each capsule? () (c) The designers of the London Eye had to consider three factors which affect the resultant force described in part (b). Two factors that increase the resultant force are: an increase in the speed of rotation an increase in the total mass of the wheel, the capsules and the passengers. Name the other factor that affects the resultant force and state what effect it has on the resultant force. () (Total 4 marks) Page 22 of 48 Q6. The diagram shows a design for a crane. The crane is controlled by a computer. The purpose of the motors and gears is to change the pulling force in the steel cable. This is done so that the jib stays horizontal whatever the size of the load or the position of the load. Use the equation in the box to answer questions (a) and (b). moment = force x perpendicular distance from the line of action of the force to the axis of rotation (a) Calculate the moment caused by the load in the position shown in the diagram. Show clearly how you work out your answer and give the unit. Moment =... (3) (b) Calculate the pulling force that is needed in the steel cable to keep the jib horizontal. Show clearly how you work out your answer. Pulling force =... N (Total 5 marks) Page 23 of 48 Q7. The diagram shows a man standing in an airport queue with his wheeled bag. (a) The man applies an upward force to the handle of his bag to stop the bag from falling. The moment of this force about the pivot is 36 Nm. Calculate the upward force the man applies to the handle of his bag. Use the correct equation from the Physics Equations Sheet. Force =... N (b) When the man lets go of the bag handle, the bag falls and hits the floor. Explain why. Page 24 of 48 (c) During his holiday the man visits the Foucault Pendulum in Paris, France. The pendulum makes 0 complete swings every 60 seconds. Calculate the frequency of the pendulum and give the unit. Use the correct equation from the Physics Equations Sheet. Frequency =... (3) (Total 7 marks) Q8. The diagram shows a G-machine. The G-machine is used in astronaut training. The G-machine moves the astronaut in a horizontal circle. (a) When the G-machine is rotating at constant speed, the astronaut is accelerating. State the name and direction of the force causing the astronaut to accelerate. Name of force... Direction of force... Page 25 of 48 (b) The force causing the astronaut to move in a circle is measured. The graph shows how the speed of the astronaut affects the force causing the astronaut to move in a circle for two different G-machines. The radius of rotation of the astronaut is different for each G-machine. Speed in metres per second (i) State three conclusions that can be made from the graph (3) (ii) The speed of rotation of G-machine is increased from 20 m/s to 40 m/s. Determine the change in force on the astronaut. Change in force =... N () Page 26 of 48 (c) Each G-machine is rotated by an electric motor. The diagram shows a simple electric motor. (i) A current flows through the coil of the motor. Explain why side A of the coil experiences a force. (ii) (iii) Draw arrows on the diagram to show the direction of the forces acting on side A of the coil and side C of the coil. When horizontal, side B experiences no force. Give the reason why. () () (d) While a G-machine is rotating, the operators want to increase its speed. What can the operators do to make the G-machine rotate faster? () Page 27 of 48 (e) The exploration of space has cost a lot of money. Do you think spending lots of money on space exploration has been a good thing? Draw a ring around your answer. Yes No Give a reason for your answer. () (Total 2 marks) Page 28 of 48 Q9. Mountain bike riders use brakes to slow down. Some mountain bikes have hydraulic brakes. Ljupco Smokovski/Shutterstock (a) What property of a liquid enables a hydraulic brake system to work? () Page 29 of 48 (b) When the rider s hand pulls on the brake lever, the master piston applies a pressure of pascals to the liquid. Using information from the diagram, calculate the force F exerted on the liquid by the master piston. Use the correct equation from the Physics Equations Sheet. Force F =... N (c) The pressure in the liquid applies a force to move each slave piston. How does the size of this force compare to the force F applied by the master piston? Give a reason for your answer. (Total 5 marks) Page 30 of 48 Q20. Musicians sometimes perform on a moving platform. Figure shows the parts of the lifting machine used to move the platform up and down. Figure (a) What type of system uses a liquid to transmit a force? () (b) The pump creates a pressure in the liquid of 8.75 x 0 4 Pa to move the platform upwards. Calculate the force that the liquid applies to the piston. Use the correct equation from the Physics Equations Sheet. Force =... N (c) The liquid usually used in the machine is made by processing oil from underground wells. A new development is to use plant oil as the liquid. Extracting plant oil requires less energy than extracting oil from underground wells. Suggest an environmental advantage of using plant oil. () Page 3 of 48 (d) Musicians often use loudspeakers. Figure 2 shows how a loudspeaker is constructed. Figure 2 The loudspeaker cone vibrates when an alternating current flows through the coil. Explain why. (4) (Total 8 marks) Page 32 of 48 Q2. (a) Figure shows a sheet of card. Figure Describe how to find the centre of mass of this sheet of card. You may draw diagrams as part of your answer. (5) Page 33 of 48 (b) Figure 2 shows a person in his wheelchair. Figure 2 AndreyPopov/iStock/Thinkstock (i) Tipping the wheelchair at a large angle may cause it to become unstable and to topple over. Explain why. (ii) Some disabled athletes use a wheelchair in sports. State two ways of changing the design of the wheelchair in Figure 2 so that it is more stable when used by a disabled athlete (Total 9 marks) Page 34 of 48 M. 300 allow mark for rearranging equation or correct substitution [2] M2. (a) any two ideas: (acceleration occurs when) the direction (of each capsule) changes velocity has direction acceleration is (rate of) change of velocity 2 (b) to(wards) the centre (of the wheel) (c) centripetal allow minor misspellings but do not credit a response which could be centrifugal (d) the greater the radius / diameter / circumference (of the wheel) the smaller the (resultant) force (required) accept the size both parts required for the mark accept converse [5] M3. (a) (line of action of) its weight falls inside its wheel base accept falls between the wheels the first two points may be credited by adding a vertical line from the centre of the X on the diagram () and labelling it weight / force / with a downwards arrow () provided there is no contradiction between what is added to the diagram and anything which may be written (so there is) no (resultant / clockwise) moment / turning effect Page 35 of 48 (b) centre of mass should be lower accept centre of gravity accept weight / mass low down not just lower the roof wheel base should be wider accept long axle(s) for wide wheel base allow bigger / larger wheel base do not credit long wheel base responses in either order [5] M4. (a) (i) centre of X directly below P and between the model aeroplanes as judged by eye but between centre of propeller of top aeroplane and canopy of bottom aeroplane example (ii) the centre of mass is (vertically) below the point of suspension / P the centre of mass is in the middle of the aeroplanes accept the centre of mass is level with the aeroplanes Page 36 of 48 (b) centre of mass of the worker and the ladder (and device) line of action of the weight is inside the base accept the centre of mass is above / within / inside the base (of the ladder and device) so there will not be a (resultant) moment accept so he / it / the ladder will not topple even if he leans over or it will (only) topple over if the line of action of the weight / the centre of mass is outside the base accept each point, either on the diagram or in the written explanation, but do not accept the point if there is any contradiction between them [6] M5. (a) (from present/recent) data/evidence/observations of (the rate of change in) Phobos /the moon s orbit () or appropriate example of data () and its correct use () (and) continued/extended/extrapolated (the pattern/trend for the next 00 million years) () example (present) distance from Phobos to Mars () (average) rate of approach () 2 (b) (it is) increasing () Phobos/the moon will be nearer (to Mars) () or the radius/circumference/diameter of the orbit of Phobos/the moon will decrease/be less only credit 2nd mark if the first mark is correct 2 (c) it will increase/be more () (because) Phobos/the moon will get/be closer to Mars/the planet () only credit 2nd mark if the first mark is correct note part(s) of this response may be included as the answer to part (b) read both before marks are awarded 2 [6] Page 37 of 48 M6. (a) 560 allow mark for clockwise (moments) = anticlockwise (moments) allow mark for correct substitution ie = W 0.5 allow mark for correct transformation ie 4 (c) newtons, N the weight of plank which has been ignored causes an anticlockwise moment which has not been considered / included in the calculation [7] M7. (a) where the mass of the object can be thought to be concentrated (b) (c) lower the C of M and make the wheelbase wider accept a practical description of how these changes could be achieved the line of action of its weight accept a vertical arrow drawn from X falls inside its wheel base accept falls between the wheels 2 therefore there is no resultant / clockwise moment [6] Page 38 of 48 M8. (a) the direction of the riders is constantly changing therefore the velocity of the riders is changing and because acceleration is the rate of change of velocity the acceleration is changing (b) to(wards) the centre (of the cylinder / rotor) (b) centripetal (b) it is reduced [6] M9. (a) allow for mark 2 Nm or newton metres do not credit nm, mn or metre newtons (b) (N) or 6 kn allow mark for accept their (a) 2.4 correctly calculated for 2 marks accept their (a) 2.4 for mark 2 [5] M0. (a) the point at which the (total) mass seems to act / appears to be concentrated accept weight for mass accept the point at which gravity seems to act do not accept a definitive state
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