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SPH3U - Forces SPH3U Dynamics Test Review Outline Format: 15 marks multiple choice, 25 marks short answer (calculate/explain) All Forces Unit Equations will be provided, Big 5 Equation sheets may be used Topics and Concepts: Textbook pages and recommended study materials: Newton’s First, Second and Third Laws Readings: pp. 119-130, 136-138, 152-160, 162-172, 175-177 inertia and mass Forces worksheet (problems combining forces and balanced and unbalanced forces kinematics) force pairs (action and reaction force FBD worksheet pairs) Newton’s First and Second Law quiz forces are vectors and can be added up like vectors class notes, example problems net force, Fnet ma http://www.physicsclassroom.com/Class/index.cfm free body diagrams (FBDs) normal force friction – static and kinetic ( F f FN ) mass, weight, force due to gravity ( Fg mg , g = 9.8 N/kg) Gm1m2 universal gravitation ( Fg ,G= r2 6.67 × 10-11 Nm2/kg2) Fundamental Forces Helpful Review Questions: Forces: p. 143 – 3, 4, 5, 6, 8, 10, 14, 16, 19, 20, 22, 23, 25, 26, 27, 29, 31, 35, 36, 37, 38, 39, 42, 44, 53, 54 p. 181 – 20, 21, 28, 32, 36, 37, 38, 39, 44, 46, 47, 48 Some Force Problems: 1. Explain what headrests, airbags and seatbelts in cars and whiplash have to do with Newton’s laws of motion. 2. Julien steps onto a dock off a boat that is tied securely and close to the dock. Meanwhile, Dylan steps off her boat when it is not yet attached to the dock. Use Newton’s laws to explain what happens in each case. 3. A block of mass 15.0 kg, starting from rest, is pulled along a rough horizontal tabletop by a constant force. The coefficient of friction (kinetic) is 0.3. It is found that this body moves a distance of 5.0 m in 4.0 s. a) What is the force of friction acting on the body? (44 N) b) What is the acceleration of the body? (0.63 m/s2) SPH3U - Forces c) What constant force is being applied to the body? (54 N) 4. Henry drives Car A, of mass 1000 kg, at 100 km/h, and brakes to a stop. Jaiden drives Car B, of equal mass, at 50 km/h and also brakes to a stop. Assume that the braking force is constant and the same for both vehicles, and compare the braking distances for the cars. (Car A’s braking distance is 4x that of Car B’s) 5. Carly drives Car C, of mass 2000 kg, at 50 km/h and brakes to a stop with the same braking force as in the previous question. Compare the braking distance of Car C to car A. (Car C’s braking distance is 2x that of Car A’s) 6. Draw FBDs for each of the following cases. Neglect air resistance. The rock is tied to a rope The rock is slowing and is pulled upward down due to friction. such that it is accelerating up. 7. Mariela and Alex pin a giant salamander (50 kg) against a wall with a force of 1500 N so that it is suspended off the ground without slipping. What is the coefficient of static friction that allows them to do this? (0.33) 8. Tatiana, floating in space at some distance above the earth’s surface, notices that the force of gravity she is experiencing from the earth is one-quarter what she would feel at the surface of the earth. How far away is she from the centre of the earth, in terms of the earth’s radius? How far above the surface of the earth is she, in terms of the earth’s radius? The radius of the earth is 6.38 × 106 m, and the mass of the earth is 5.98 × 1024 kg. (twice the radius, one radius) 9. Xhorxhia, on a sunny resort beach, measures the gravitational attraction between her and a mysterious stranger 50 m away to be 1.067 × 10-10 N. Assuming she has a mass of 50 kg, what is the mass of the mysterious stranger? (80 kg)

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posted: | 7/10/2011 |

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