1. Motion, forces and energy
A section of Physics, 5054
Listing 10 of 1150 questions
A spacecraft of mass 300 kg is moving in a straight line in space, at a speed of 8000 m / s. Calculate the momentum of the spacecraft. momentum = kg m / s The fuel on the spacecraft explodes and the spacecraft splits into two parts. The direction in which the parts move does not change. After the explosion, the speed of the front part increases to 9000 m / s. It has a mass of 150 kg. Calculate the speed of the rear part after the explosion. speed = m / s The total kinetic energy of the two parts after the explosion is greater than the original kinetic energy of the spacecraft. State the energy transfer that occurs in the explosion. The explosion lasts for 0.20 s. Calculate the average force on the front part during this time. force = N
5054_w23_qp_22
THEORY
2023
Paper 2, Variant 2
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shows a device for punching holes in a piece of paper. A person applies a force F at the end of the arm. Just before the hole is made in the paper, the arm is at rest. paper steel rod pivot arm 1.0 cm 8.0 cm force F metal base Just before the hole is made, the force upwards on the steel rod is 7.2 N. Calculate the value of F. Use the distances marked on . F = The steel rod pushes the paper into the hole in the metal base with a force of 7.2 N. The end of the steel rod has an area of 2.8 × 10 –5 m2. Calculate the pressure exerted on the paper. State the formula that you use in your calculation. pressure = The force downwards on the paper due to the rod and the force upwards on the rod due to the paper are related by Newton’s third law. State Newton’s third law.
5054_s08_qp_2
THEORY
2008
Paper 2, Variant 0
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10 shows a car braking system. The brake fluid is an oily liquid. brake pedal master piston pivot brake drum brake shoe return spring master cylinder brake fluid slave pistons pivot The brake drum rotates with the wheel of the car. Explain how pushing the brake pedal makes the brake shoes rub against the drum. The cross-sectional area of the master piston is 2.0 cm2. A force of 140 N is applied to the master piston. Calculate the pressure created in the brake fluid by the master piston. pressure = N / cm2 The cross-sectional area of each slave piston is 2.8 cm2. Calculate the force exerted on each slave piston by the brake fluid. force = The force exerted on the master piston is greater than the force applied by the foot on the brake pedal. Using the principle of moments, explain this. shows a master cylinder sealed at one end. Instead of brake fluid, the cylinder contains air. d piston of area 2.0 cm2 sealed end air When a force is applied to the piston, the length d changes from 6.0 cm to 4.0 cm. The pressure of the air increases but the temperature stays constant. Describe how the molecules of the air exert a pressure. Explain why the pressure increases even though the temperature stays constant. The initial pressure of the air inside the cylinder is 1.0 × 105 Pa. Calculate the final pressure of the air. State the formula that you use in your calculation. pressure = Air bubbles form in the brake fluid of . State the effect this has on the braking system.
5054_s10_qp_21
THEORY
2010
Paper 2, Variant 1
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shows part of a hydraulic jack used to lift the front of a car. front of car arm cylinder large piston oil small piston force exerted by operator handle pivot pivot (not to scale) The operator pulls the handle and causes a force of 50 N to act on the small piston. The force exerted by the oil on the large piston increases by F. The large piston moves and rotates the arm about the pivot. This raises the front of the car. The cross-sectional area of the small piston is 1.5 cm2. The cross-sectional area of the large piston is 5.0 cm2. Calculate the pressure in the oil caused by the force on the small piston, pressure = the value of F. F = Explain why the large piston moves through a shorter distance than the small piston. The efficiency of the jack is 75%. Explain what is meant by efficiency.
5054_s14_qp_22
THEORY
2014
Paper 2, Variant 2
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A student pushes a drawing pin into a wooden board, as shown in . finger drawing pin wooden board The area of the pin in contact with the finger is 5.0 × 10−5 m2. The student pushes downwards with a force of 26 N. The mass of the drawing pin is very small. Calculate the pressure exerted by the finger on the drawing pin. pressure = Pa Compare the force exerted by the finger on the drawing pin with the force exerted by the drawing pin on the wooden board. Explain why the drawing pin goes into the wooden board but not into the finger. shows water emerging from a plastic bag that contains a number of small holes. A B Explain why the water emerges from each hole in a direction at right angles to the surface of the bag. The holes at A and B are the same size. Explain why the water emerges faster from the hole at A than from the hole at B.
5054_s23_qp_21
THEORY
2023
Paper 2, Variant 1
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Questions Discovered
1150