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Transcript
An object is moving down. How does the tension T in the string compare with the weight "mg" of the object? A: T=mg B: T > mg C: T < mg D: Not enough information given. v v v f i a t t f ti When an object moves in a circle, is its velocity changing? Assume that the speed of the bowling ball remains almost constant and find the direction of the acceleration of the ball assuming that the direction of the acceleration is the same as the direction of the velocity change vector. Two similar isosceles triangles at R V x at V x V R V a t a V2 a R Vi x R V2 a R a R 2 2 mV F ma m 2 R R F R V a An object moves in a circular path with constant speed. Which of the following statements is true concerning the object? A. Its velocity is constant, but acceleration is changing B. Its acceleration is constant, but velocity is changing C. Both its velocity and acceleration are changing D. Both its velocity and acceleration remain constant V A car passes over a hill in the road that has a circular cross-section. How does the force exerted by the road on the car compare with the weight of the car? A: N = mg B: N > mg C: N < mg D: Not enough information given. V A car passes over a low spot in the road that has a circular crosssection. How does the force exerted by the road on the car compare with the weight of the car? A: N = mg B: N > mg C: N < mg D: Not enough information given. A mass is hanging from a rope and swinging around a circular path at constant speed. The situation is shown in the figure. Draw a free body diagram Support rope mass circular path Pendulum Suspended from Spring Scale A bob is hung by a string, attached to a spring scale which is suspended from a stand. First note the reading on the spring scale when the bob is not moving. The bob and string will then be pulled back so that the string makes an angle theta with the vertical. The bob will then be released and allowed to swing. Predict what will happen to the reading on the spring scale at the bottom of the swing (more, less or same as when the object is at rest). L s A: s = L B: s > L C: s < L A: S = L B: S > L C: S < L A small wheel and a large wheel are connected by a belt. The small wheel is turned at a constant angular velocity s. How does the magnitude of the angular velocity of the large wheel L compare to that of the small wheel? There is a bug S on the rim of the small wheel and another bug L on the rim of the large wheel. How do their speeds compare? Homework (due Monday) Read Sections 7.4 Examples!!! Problems # 21, 25, 27, 28, 32 Quiz V A car passes over a hill in the road that has a circular cross-section with a radius of 30m. The speed of the car at the top of the hill is 10 m/s. What is the force exerted by the seat of the car on a 60kg passenger when the car is at the top pf the hill?