Sci. 9.docx

Republic of the Philippines Department of Education Region V- Bicol Division of Camarines Norte Sta. Elena District

STA. ELENA INTEGRATED SCHOOL 4 PERIODICAL EXAMINATION IN SCIENCE 7 th

Name:______________________________________ Date:_______________________ Grade& Section:___________ Score:__________ Directions: Read and analyze the following questions carefully. Choose and encircle the letter that best describe your answer. 1. Which of the following is a necessary condition for the total momentum of a system to be conserved? a. Kinetic energy must not change c. the system must be at rest b. No net external force acts on the system d. only the force of gravity acts on the system 2. A25 kg girl is riding a 5 kg bike with a velocity of 5m/s going east. What is the total momentum of a girl and a bike together? a. 100 kg m/s b. 125 kg m/s c. 150 kg m/s d. 200 m/s 3. A bus and a car are travelling along EDSA having the same velocity. Which of the two vehicles would have greater momentum? a. The bus c. the car b. both have the same momentum d. cannot be easily determined For question 4 and 5, refer to the table below: Vehicle Mass (kg) Velocity (m/s) Jeepney 2000 10 Motorcycle 300 20 4. In the table above, what is the momentum of the jeepney? a. 6,000 kg m/s b. 40,000 kg m/s c. 20,000 kg m/s d. 3,000 kg m/s 5. Which has greater momentum, the jeepney or the motorcycle? a. The jeepney c. both have the same momentum b. The motorcycle d. cannot be easily determined 6. Two billiards balls approach each other with the same speed. If they collide in a perfectly elastic collision, what would be their velocities after collision? a. Zero c. same in magnitude but opposite in direction b. Same in magnitude and direction c. different in magnitude and opposite in direction 7. A free falling ball is equipped with a speedometer, by how much would its speed reading increase for every second? a. 0 m/s b. 9.8 m/s c. 10 m/s d. 20 m/s 8. The motion of an object with constant acceleration is also known as___________. a. Motion b. uniform motion c. constant motion d. uniformly accelerated motion 9. What is the energy of a motorcycle moving slowly at the top of a hill? a. Entirely kinetic c. entirely gravitational b. Entirely potential d. both kinetic and potential 10. Which event does NOT describe potential energy being changed into kinetic energy? a. A box sliding down a ramp c. a pen spring compressed b. A mango falling from a crate d. a stretched rubber band got loosened 11. Which event illustrates the direct transformation of potential to kinetic energy? a. A basketball player catches a flying ball b. a kalesa moves from rest c. Kathy’s arrow is released from its bow d. the spring mechanism of a toy is stretched until it locked 12. Which sequence of energy transformation best describes what happens when you switch on your battery-run radio? a. Mechanical Energy- Electrical Energy- Sound Energy b. Mechanical Energy- Chemical Energy- Sound Energy c. Chemical Energy- Electrical Energy- Sound Energy d. Chemical Energy- Mechanical Energy- Sound Energy 13. Which among the forms of energy is considered as potential energy? a. Chemical energy b. radiant energy c. sound energy d. thermal energy

14. Which of the following happens to a coconut that falls freely? a. Loses potential energy and gain kinetic energy b. Loses both potential and kinetic energy c. Gains potential energy and loses kinetic energy d. Gains both potential and kinetic energy 15. A torch light fell from a watch tower. The potential energy of the torch light at the highest point compared to its kinetic energy at the lowest point is_______. a. Lesser b. equal c. greater d. not related 16. The potential energy of a 1-kg object on a top of a hill is 18J. What is the velocity in m/s just before it hits the bottom of the hill? a. 36 b. 18 c. 6 d. 3 17. If 500 cal. of heat are added to a gas, and the gas expands doing 500 J of work on its surroundings, what is the change in the internal energy of the gas? a. 1555J b. 5915 J c. 5159 J d. 1595 J 18. An ideal gas is compressed without allowing any heat to flow into or out of the gas. What will happen to the gas in this process? a. The temperature increases since no heat flows during the process b. The temperature decreases since heat flow during the process c. The temperature remains the same since heat flows in and out of the process d. The temperature could not be determined since heat is absorbed during the process 19. Is it possible to change the temperature of a glass of water by stirring the water, even though the glass is insulated from its surroundings? a. No, the temperature will not affect the temperature of the water b. No, insulation prevents the change of temperature of the water c. Yes, stirring the water increases its internal energy causing the increase of its temperature d. Yes, stirring the water decreases its internal energy causing of its temperature 20. Mang Fermin, a carpenter, is planning a piece of wood with his planar. After a few minutes, he observed that it is hot. Is there an evidence of heat transfer? a. There is no evidence b. Yes, hotness means there is an increase in the temperature c. Yes, hotness means there is a decrease in temperature d. No, hotness is not related to a change in temperature 21. How does water from the deep well move upward? a. It occurs naturally c. It is a spontaneous process b. It uses water heat pump d. it flows from higher temperature to cooler temperature 22. Given the following, mechanisms, which best describes correct sequence of the refrigeration cycle? i. Compression iii. Expansion ii. Condensation iv. Evaporation a. i,ii,iii,iv b. ii,iii,iv,I c. iii,iv,i,ii d. iv,iii,i,ii 23. What is the function of heat engine? a. It converts chemical energy to mechanical energy b. It converts thermal energy to mechanical energy c. It converts mechanical energy to chemical energy d. It converts thermal energy into chemical energy 24. How can air conditioning unit functions as heater during cold days and cooler during hot days? i. It cools the inside of the house and heats the outside ii. It takes heat from the air outside to warm the inside a. I only b. ii only c. I and ii d. none of the choices 25. In which of the following units is electrical consumption measured by electric companies for our household consumption in our house? a. Kilowatt b. volt c. megawatt d. kilowatt 26. In power stations generating electricity, power is measured in_______. a. Joule b. kilojoule c. kilowatt d. megawatt 27. Why do power stations generate AC, and not DC? a. It is safer to generate, safer, and more economical to transmit AC than DC b. Transformer work with AC c. AC is used in mobile devices and gadgets d. AC is more efficient and economical 28. Transformers are used to raise the voltage along the substations and lower for residential consumption. What kinds of transformers are used to raise the voltage? a. Step-up b. step-down c. neither of the two d. both

29. Shane turned on a lamp switch in her room. Which of the following is the correct path of electrical power that can be traced back to the source? a. Power plant-transmission substation- distribution substation-residences b. Transmission substation-power plants-residences- distribution substation c. Residence-distribution substations-power plants-transmission substation d. Distribution substation-transmission substation-power plants- residences 30. You made an electric motor in school. When you tested it by using 4 dry cells, the armature turned very fast. What should you do to make it turn slower? a. Use a bigger magnet b. Remove one of the dry cells c. Increase the number of turns in the coil of wire d. Decrease the distance between the magnetic poles 31. What energy transformation takes place in a generator? a. Electrical to mechanical c. mechanical to electrical b. Heat to mechanical d. chemical to mechanical 32. A bag drops some distance and gains 90 J of kinetic energy. Considering air resistance, how much gravitational potential energy did the bag lose? a. More than 90 J b. exactly 90 J c. less than 90 J d. none of the choices TEST II Directions: Read and analyze the following questions carefully. Use calculator in solving the problem. You can use the back in solving your answer. A ball rolls off a 1.0 m high table and lands on the floor, 3.0 m away from the table. 33. How long is the ball in the air? 34. With what horizontal velocity did the ball roll off the table? 35. What is the vertical velocity of the ball just before it hits the floor? 36. What is the horizontal velocity of the ball just before it hits the floor? 37.A carpenter tosses a shingle off a 9.4 m high roof, giving it an initial horizontal velocity of 7.2 m/s. What is the final vertical velocity of the ball? 38-39 You serve volleyball with a mass of 2.1 kg. The ball leaves your hand with a speed of 30 m/s. What is the kinetic energy of the ball? 40-41 A cinder blocks is sitting on a platform 20 m high. It weighs 7.9 kg. Calculate the potential energy of the cinder block. 42-47. Supply the table with the final answer obtained from the computation to show the relationship existing among thermal efficiency, temperature/energy in hot reservoir and temperature/ energy in cold reservoir. Temperature/energy in cold Temperature/ energy in hot Thermal Efficiency reservoir reservoir 250K 500K 650J 259J

1054J 677J

300C

880C

230 K

700K

770C

930C

48-50 All the computers in the ICT room are in use for five hours every day and together use 8.3kW. How much energy is used in a day?

Prepared By: Ms. A. Gobless!!! Happy Vacation!