Dynamics (Work and Energy) Tutorial

8/16/2019 Dynamics (Work and Energy) Tutorial

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MIET7296 Apply Scientific Principles

College of Science, Engineering and Health Class Notes Prepared by Yadana Wai

School of Engineering (TAFE) 1

Work and Energy (Tutorial)1. Define the work done and energy in mechanical engineering.

2. A horse pulls a cart offering 600N resistance for a distance of 200 m at a constant velocity.

(i) The work done by the horse

(ii) The total work done by moving the wagon 200 m.

Answer: (i) 120 kJ (ii) 0J

3. A man cleaning a floor pulls a vacuum cleaner with a force of magnitude F =50.0 N at an

angle of 30.0° with the horizontal as shown below. Calculate the work done by the force on

the vacuum cleaner as the vacuum cleaner is displaced 3.00 m to the right.

Answer: 130J

4. A man wishes to load a refrigerator onto a truck using as ramp, as shown below. He claims

that less work would be required to load the truck if the length L of the ramp were increased.

Is his statement valid?






5. In the sport of pole vaulting, the jumper’s centre of mass must clear the pole. Assume that a

59-kg jumper must raise the centre of mass from 1.1 m off the ground to 4.6 m off the ground.

What is the jumper’s gravitational potential energy at the top of the bar relative to where the

jumper started to jump?

Answer: 2 kJ

6. Find the kinetic energy of a 48-g dart travelling at a speed of 3.4 m/s.

Answer: 0.28J






7. If the speed of an object is doubled then its kinetic energy is _______.

(a) Doubled

(b) Halved

(c) Tripled

(d) Quadrupled

8. An iron sphere of mass 30 kg has the same diameter as an aluminium sphere whose mass is

10.5 kg. The spheres are dropped simultaneously from a cliff. When they are 10 m from theground, they have the same _______.

(a) Kinetic energy

(b) Potential energy

(c) Acceleration

(d) Momentum

9. A 1 kg mass has a kinetic energy of 1 joule when its speed is _________________.

(a) 0.45 m/s

(b) 1 m/s

(c) 1.4 m/s

(d) 4.4 m/s

10. An object of mass 1 kg has gravitational potential energy of 1 joule relative to the ground

when it is at a height of _______.

(a) 0.102 m

(b) 1 m

(c) 9.8m

(d) 32m

11. Kinetic energy can be described as ______________.

(a) Stored energy

(b) Energy in motion(c) A chemical reaction

(d) Connected energy

12. An example of Potential Energy would be __________

(a) Moving car

(b) A battery

(c) A book resting on a table

(d) Both (b) and (c)

13. Greg applies a force of 100 N to move a box 5 meters. How much work did he do?

(a) 100 J

(b) 5 J

(c) 500 J

(d) 500 N






14. Which of the following is true at the point where you reach the top of your jump on a

trampoline?

(a) The mechanical energy is zero.

(b) The potential energy is at a maximum.

(c) The kinetic energy and potential energy are equal.

(d) The potential energy is zero.

15. What is the ability to do work called?(a) Movement

(b) Power

(c) Energy

(d) Force

16. Why are you not doing any work when you are carrying your backpack to class at a constant

speed?

17. Compare energy and work. What does one have to do with the other?

18. What are two things that must happen for work to be done?

19. A worker does 25 J of work lifting a bucket, then sets the bucket back down in the same place.

What is the total net work done on the bucket?

(a) –25 J

(b) 25J

(c) 0J

(d) 50J

20. A horizontal force of 200 N is applied to move a 55 kg television set across a 10 m level

surface. What is the work done by the 200 N force on the television set?

(a) 550J(b) 6000J

(c) 2000J

(d) 11000J

21. What is the kinetic energy of a 0.135 kg baseball thrown at 40.0 m/s?

(a) 54.0 J

(b) 108 J

(c) 87.0 J

(d) 216 J

22. Gravitational potential energy is always measured in relation to _____________.

(a) Kinetic energy

(b) Total potential energy

(c) Mechanical energy

(d) A zero level






23. An object weighing 15 newtons is lifted from the ground to a height of 0.22 meter. The

increase in the object’s gravitational potential energy is approximately ___________.

(a) 310J

(b) 32 J

(c) 3.3J

(d) 0.34J

24. As an object falls freely, the kinetic energy of the object __________.(a) Decreases

(b) Increases

(c) Remain the same

25. It is given that 1 gallon gasoline has energy content of 125,000 BTU and 1 BTU ~ 1,000 J

(actually 1,055.056 J). Suppose the energy in gasoline was converted completely into kinetic

energy of a 1000 kg car. How fast would the car be going after burning 1 gallon of gas?

(a) 5 m/s

(b) 10 m/s

(c) 50 m/s

(d) 100 m/s(e) 500 m/s

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Dynamics (Work and Energy) Tutorial