10. Conservation of Energy

Intro to Conservation of Energy

Open Question
(I) A novice skier, starting from rest, slides down an icy frictionless 8.0° incline whose vertical height is 115 m. How fast is she going when she reaches the bottom?
Multiple Choice
A $10 kg$ block slides down a $3.0 m$ tall frictionless ramp. How fast will the block be moving at the bottom? Use energy concepts to solve this problem.
Open Question
(II) In the high jump, the kinetic energy of an athlete is transformed into gravitational potential energy without the aid of a pole. With what minimum speed must the athlete leave the ground in order to lift his center of mass 2.10 m and cross the bar with a speed of 0.50 m/s?
Open Question
(II) A sled is initially given a shove up a frictionless 18.0° incline. It reaches a maximum vertical height 1.22 m higher than where it started at the bottom. What was its initial speed?
Open Question
(II) A 62-kg trampoline artist jumps upward from the top of a platform with a vertical speed of 4.5 m/s. (a) How fast is he going as he lands on the trampoline, 2.0 m below (Fig. 8–32)? <IMAGE>
Open Question
(I) A 16.0-kg child descends a slide 2.20 m high and, starting from rest, reaches the bottom with a speed of 1.15 m/s. How much thermal energy due to friction was generated in this process?
Open Question
(a) A 3.0-g locust reaches a speed of 3.0 m/s during its jump. What is its kinetic energy at this speed?
(b) If the locust transforms energy with 35% efficiency, how much energy is required for the jump?
Open Question
Proper design of automobile braking systems must account for heat buildup under heavy braking. Calculate the thermal energy dissipated from brakes in a 1500-kg car that descends a 17° hill. The car begins braking when its speed is 95 km/h and slows to a speed of 35 km/h in a distance of 0.30 km measured along the road.
Open Question
A 1.0 kg mass that can move along the x -axis experiences the potential energy U=(x²−x) J, where x is in m. The mass has velocity v𝓍=3.0 m/s at position x=1.0 m . At what position has it slowed to 1.0 m/s?
Open Question
FIGURE 10.23 showed the potential-energy curve for the O2 molecule. Consider a molecule with the energy E1 shown in the figure.a. What is the maximum speed of an oxygen atom as it oscillates back and forth? Don't forget that the kinetic energy is the total kinetic energy of the system. The mass of an oxygen atom is 16 u, where 1u=1 atomic mass unit =1.66×10(to the poer of)−27 kg .
Open Question
The spring shown in FIGURE P10.54 is compressed 50 cm and used to launch a 100 kg physics student. The track is frictionless until it starts up the incline. The student's coefficient of kinetic friction on the 30° incline is 0.15. a. What is the student's speed just after losing contact with the spring?
Open Question
Two blocks with masses mA and mB are connected by a masslessstring over a massless, frictionless pulley. Block B, which ismore massive than block A, is released from height h and falls. b. A 1.0 kg block and a 2.0 kg block are connected by a masslessstring over a massless, frictionless pulley. The impact speedof the heavier block, after falling, is 1.8 m/s. From how highdid it fall?
Open Question
Two blocks with masses mA and mB are connected by a masslessstring over a massless, frictionless pulley. Block B, which ismore massive than block A, is released from height h and falls.a. Write an expression for the speed of the blocks just as blockB reaches the ground.
Open Question
A block of mass m slides down a frictionless track, then around the inside of a circular loop-the-loop of radius R . From what minimum height h must the block start to make it around without falling off? Give your answer as a multiple of R.
Open Question
A 50 g mass is attached to a light, rigid, 75-cm-long rod. The other end of the rod is pivoted so that the mass can rotate in a vertical circle. What speed does the mass need at the bottom of the circle to barely make it over the top of the circle?