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At the bottom of an air track tilted at angle θ, a glider of mass m is given a push to make it coast a distance d up the slope as it slows clown and stops. Then the glider comes back down the track to its starting point. Now the experiment is repeated with the same original speed but with a second identical glider set on top of the first. The airflow from the track is strong enough to support the stacked pair of gliders so that the combination moves over the track with negligible friction. Static friction holds the second glider stationary relative to the first glider throughout the motion. The coefficient of static friction between the two gliders is µ,. What is the change in mechanical energy of the two-glider—Earth system in the up- and down-slope motion after the pair of gliders is released? Choose one. (a) –2µ,mg (b) —2mgd cos (c) –2µ,mgdcos θ (d) 0 (e) +2µ.,mgd cos θ
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Chapter 8 Solutions
EBK PHYSICS FOR SCIENTISTS AND ENGINEER
- If the net work done by external forces on a particle is zero, which of the following statements about the particle must be true? (a) Its velocity is zero. (b) Its velocity is decreased. (c) Its velocity is unchanged. (d) Its speed is unchanged. (e) More information is needed.arrow_forwardAt the bottom of an air track tilted at angle , a glider of mass m is given a push to make it coast a distance d up the slope as it slows down and stops. Then the glider comes back down the track to its starting point. Now the experiment is repeated with the same original speed but with a second identical glider set on top of the first. The airflow from the track is strong enough to support the stacked pair of gliders so that the combination moves over the track with negligible friction. Static friction holds the second glider stationary relative to the first glider throughout the motion. The coefficient of static friction between the two gliders is s. What is the change in mechanical energy of the two-glider-Earth system in the up- and down-slope motion after the pair of gliders is released? Choose one. (a) 2smg (b) 2mgd cos (c) 2smgd cos (d) 0 (e) +2smgd cosarrow_forwardA particle moves in a medium under the influence of a retarding force equal to mk(υ3+ a2υ), where k and a are constants. Show that for any value of the initial speed the particle will never move a distance greater than π/2kaand that the particle comes to rest only for t → ∞.arrow_forward
- Why is the following situation impossible? In a new casino, a supersized pinball machine is introduced. Casino advertising boasts that a professional basketball player can lie on top of the machine and his head and feet will not hang off the edge! The ball launcher in the machine sends metal balls up one side of the machine and then into play. The spring in the launcher (Fig. P6.60) has a force constant of 1.20 N/cm. The surface on which the ball moves is inclined = 10.0 with respect to the horizontal. The spring is initially compressed its maximum distance d = 5.00 cm. A ball of mass 100 g is projected into play by releasing the plunger. Casino visitors find the play of the giant machine quite exciting.arrow_forwardA child of mass m starts from rest and slides without friction from a height h along a slide next to a pool (Fig. P7.27). She is launched from a height h/5 into the air over the pool. We wish to find the maximum height she reaches above the water in her projectile motion. (a) Is the childEarth system isolated or nonisolated? Why? (b) Is there a nonconservative force acting within the system? (c) Define the configuration of the system when the child is at the water level as having zero gravitational potential energy. Express the total energy of the system when the child is at the top of the waterslide. (d) Express the total energy of the system when the child is at the launching point. (e) Express the total energy of the system when the child is at the highest point in her projectile motion. (f) From parts (c) and (d), determine her initial speed vi at the launch point in terms of g and h. (g) From parts (d), (e), and (f), determine her maximum airborne height ymax in terms of h and the launch angle . (h) Would your answers be the same if the waterslide were not frictionless? Explain. Figure P7.27arrow_forwardEstimate the kinetic energy of the following: a. An ant walking across the kitchen floor b. A baseball thrown by a professional pitcher c. A car on the highway d. A large truck on the highwayarrow_forward
- a block is released from rest at height d = 40 cm and slides down a frictionless ramp and onto a first plateau, which has length d and where the coefficient of kinetic friction is 0.50. If the block is still moving, it then slides down a second frictionless ramp through height d/2 and onto a lower plateau, which has length d/2 and where the coefficient of kinetic friction is again 0.50. If the block is still moving, it then slides up a frictionless ramp until it (momentarily) stops. Where does the block stop? If its final stop is on a plateau, state which one and give the distance L from the left edge of that plateau. If the block reaches the ramp, give the height H above the lower plateau where it momentarily stops.arrow_forwardA 5 kg blue block is released from rest at point A (3m high) and slides down a track. The track consists of acurved ramp and a horizontal surface seamlessly connected. The whole track is frictionless except for theportion between point B and C, which has a length of 6m. The coefficient of kinetic friction is µk = 0.35.(a) Please find out the velocity of the blue block when it arrives at the bottom of the ramp. .(b) Please find out whether the block can pass through the rough region BC. If you believe it can passthrough, please find out its speed when it arrives at point C. If you believe it cannot pass through andstop somewhere on the track, please identify its final position with the distance to point B..(c) Determine how much heat is generated at the rough surface due to friction. .arrow_forwardA box weighing 3.9 kg is initially at rest on a horizontal floor. It is then pushed in a straight line for 1.2 m by a girl exerting a horizontal force with a magnitude 36 N. What is the final speed of the box if there if no friction between the floor and the box? What is the final speed if a coeffient 0.30 would be introduced between the floor and the box?arrow_forward
- pleasearrow_forwardYou decide to launch a rockof mass m1 using a tube containing a spring of spring constant k. When the spring is at equilibrium, it fills the entire tube. To launch a rock, you push it into the tube, compressing the spring a distance d, at which point a locking mechanism holds the spring(and the rock) in place. When the lockis released, the spring pushes the rock to the end of the tube where it will be launched into the air. The coefficient of kinetic friction between the rock and the inside surface of the tube is given by μk. You setup the launcher at an angle q above the horizontal with the spring end buried such that when the spring is compressed and locked, the rock is at ground level. a)Find the work done on the rock by non-conservative forces as it moves from the point of release to the end of the tube. Express your answer in terms of μk, m1, q, d, and any necessaryconstants. b) Find the velocity of the rockvfas it exits the launch tube in terms of μk, k, m1, q, d, and any…arrow_forwardA crate is pushed up a frictionless inclined plane with initial speed of 4 m/s. The angle of incline is 30 degrees. (a) What is its speed when it gets back to the bottom? (b) How far up the plane does the block go? (c) How long does it take to get there?arrow_forward
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