## 2.4. dynamics

Question Number. 1. As an object slides down a slope, its.

Option A. kinetic energy increases and its potential energy increases.

Option B. kinetic energy increases and its potential energy decreases.

Option C. kinetic energy decreases and its potential energy increases.

Correct Answer is. kinetic energy increases and its potential energy decreases.

Explanation. Potential energy is converted into kinetic energy.

Question Number. 2. A single fixed pulley (discounting friction etc) has a mechanical advantage of.

Option A. 2.

Option B. 1/2.

Option C. 1.

Correct Answer is. 1.

Explanation. NIL.

Question Number. 3. What is the ratio of load to effort called?.

Option A. Mechanical advantage.

Option B. Velocity ratio.

Option C. Mechanical ratio.

Correct Answer is. Mechanical advantage.

Explanation. NIL.

Question Number. 4. 1 kW is.

Option A. 3413 BTU per hour.

Option B. 1.56 HP.

Option C. 360 Joules.

Correct Answer is. 3413 BTU per hour.

Explanation. 1 BTU = 0.293 W. 1 W = 1/0.293 BTU = 3.413 BTU. 1 kW = 3413 BTU.

Question Number. 5. The tension in the cable of a crane is 2500 N and it lifts a load through 50m, what is the work done on the load?.

Option A. 1.25 * 10 J5.

Option B. 500 J.

Option C. 12.5 kJ.

Correct Answer is. 1.25 * 10 J5.

Explanation. NIL.

Question Number. 6. What is the kinetic energy of an aircraft of mass of 2 metric tonnes and has a velocity of 2m/s?.

Option A. 8 kJ.

Option B. 4 kJ.

Option C. 2 kJ.

Correct Answer is. 4 kJ.

Explanation. Kinetic energy = 1/2mV. Only the V is squared. 2 metric tonnes = 2000 kg.

Question Number. 7. The work done in lifting a mass of 2000 kg vertically to a height of 40 metres is.

Option A. 80 kJ.

Option B. 784.8 kJ.

Option C. 500 kJ.

Correct Answer is. 784.8 kJ.

Explanation. Work done = Force * distance (force = mass * gravity). Wd = 2000 * 10 * 40 = 800,000 approx. (answer is slightly less because g = 9.81, not 10).

Question Number. 8. If a machine has a mechanical advantage of 10 and a velocity ratio of 20. The efficiency of the machine is.

Option A. 200%.

Option B. 0.5.

Option C. 2.

Correct Answer is. 0.5.

Explanation. 10 times the force out and only 1/20th speed, it must have an efficiency of a 1/2. (100% efficient it would have 10 times the force and 1/10th the speed - straight trade of force for speed).

Question Number. 9. 1 Watt =.

Option A. 1kg/h.

Option B. 1 Joule/s.

Option C. 1 HP.

Correct Answer is. 1 Joule/s.

Explanation. 1 Watt = 1 Joule/second.

Question Number. 10. How would you work out the work done by a machine assuming it is 100% efficient?.

Option A. Input and output.

Option B. Mechanical advantage and output.

Option C. Mechanical advantage and input.

Correct Answer is. Mechanical advantage and input.

Explanation. Assuming the 'input' means input force, to calculate the work done you will need the input force and the mechanical advantage of the machine to calculate the output force and distance (Work done = force * distance of output).

Question Number. 11. Ignoring friction, if you let an object slide down a slope, at the bottom.

Option A. the potential energy is equal to the kinetic energy.

Option B. the potential energy is more than the kinetic energy.

Option C. the kinetic energy is more than the potential energy.

Correct Answer is. the kinetic energy is more than the potential energy.

Explanation. All potential energy is converted to kinetic energy.

Question Number. 12. 1 HP = 33000 ft.lbs/min or 500 ft.lbs/s or.

Option A. 736 Watts.

Option B. 746 Watts.

Option C. 1360 Watts.

Correct Answer is. 746 Watts.

Explanation. 1 HP = 746 Watts.

Question Number. 13. A force of 15N is needed to move a body of mass 30kg along a footpath with uniform velocity. Find the coefficient of dynamic friction.(take g as 10m/s/s).

Option A. 1/20.

Option B. 1/2.

Option C. 20.

Correct Answer is. 1/20.

Explanation. NIL.

Question Number. 14. A mass of 400kg moves 27 metres with a force of 54N. What is the work produced?.

Option A. 10.1kJ.

Option B. 583.2kJ.

Option C. 1458J.

Correct Answer is. 1458J.

Explanation. NIL.

Question Number. 15. The SI unit of Power is the.

Option A. Volt.

Option B. Pascal.

Option C. Watt.

Correct Answer is. Watt.

Explanation. NIL.

Question Number. 16. What is 1 joule in calories?.

Option A. 4.186.

Option B. 252.

Option C. 0.239.

Correct Answer is. 0.239.

Explanation. NIL.

Question Number. 17. If you push an object with a force of 5 N for 10 m in 4 seconds, how much power is used?.

Option A. 12.5 watts.

Option B. 8 watts.

Option C. 200 Watts.

Correct Answer is. 12.5 watts.

Explanation. NIL.

Question Number. 18. What is the Kinetic Energy of a 2 kg object moving at a velocity of 12 m/s?.

Option A. 24 Joules.

Option B. 288 Joules.

Option C. 144 Joules.

Correct Answer is. 144 Joules.

Explanation. NIL.

Question Number. 19. A mass of 3kg weighs approximately.

Option A. 0.675 N.

Option B. 6.6 LB.

Option C. 1.3 LB.

Correct Answer is. 6.6 LB.

Explanation. 1 kg = 2.2 lb. So 3 kg = 3 * 2.2 = 6.6 lb.

Question Number. 20. Power is the rate of doing work. It is measured in.

Option A. Watts/Seconds.

Option B. Joules/Seconds.

Option C. Joules * Seconds.

Correct Answer is. Joules/Seconds.

Explanation. NIL.

Question Number. 21. A 6000 kg engine is lifted off a wing to a height 0.5 metres and then pushed across the hangar 24 meters. The force required to push the trolley is 12 kN. What is the work done to move the trolley?.

Option A. 298kJ.

Option B. 84MJ.

Option C. 288kJ.

Correct Answer is. 288kJ.

Explanation. NIL.

Question Number. 22. A ball is dropped from rest. What is its speed after 4 seconds? (Take g as 10m/s/s).

Option A. 80m/s.

Option B. 40m/s.

Option C. 20m/s.

Correct Answer is. 40m/s.

Explanation. NIL.

Question Number. 23. 1 KW is equal to.

Option A. 1.34 HP.

Option B. 1000 Joules.

Option C. 252 BTU.

Correct Answer is. 1.34 HP.

Explanation. NIL.

Question Number. 24. Ten kilograms is expressed numerically as.

Option A. 1 Mg.

Option B. 10 K.

Option C. 10 kg.

Correct Answer is. 10 kg.

Explanation. 10 kilograms = 10 kg.

Question Number. 25. An object accelerating down a slope would gain kinetic energy.

Option A. less than the potential energy lost.

Option B. greater than the potential energy lost.

Option C. equal to the potential energy lost.

Correct Answer is. equal to the potential energy lost.

Explanation. NIL.

Option A. kinetic energy increases and its potential energy increases.

Option B. kinetic energy increases and its potential energy decreases.

Option C. kinetic energy decreases and its potential energy increases.

Correct Answer is. kinetic energy increases and its potential energy decreases.

Explanation. Potential energy is converted into kinetic energy.

Question Number. 2. A single fixed pulley (discounting friction etc) has a mechanical advantage of.

Option A. 2.

Option B. 1/2.

Option C. 1.

Correct Answer is. 1.

Explanation. NIL.

Question Number. 3. What is the ratio of load to effort called?.

Option A. Mechanical advantage.

Option B. Velocity ratio.

Option C. Mechanical ratio.

Correct Answer is. Mechanical advantage.

Explanation. NIL.

Question Number. 4. 1 kW is.

Option A. 3413 BTU per hour.

Option B. 1.56 HP.

Option C. 360 Joules.

Correct Answer is. 3413 BTU per hour.

Explanation. 1 BTU = 0.293 W. 1 W = 1/0.293 BTU = 3.413 BTU. 1 kW = 3413 BTU.

Question Number. 5. The tension in the cable of a crane is 2500 N and it lifts a load through 50m, what is the work done on the load?.

Option A. 1.25 * 10 J5.

Option B. 500 J.

Option C. 12.5 kJ.

Correct Answer is. 1.25 * 10 J5.

Explanation. NIL.

Question Number. 6. What is the kinetic energy of an aircraft of mass of 2 metric tonnes and has a velocity of 2m/s?.

Option A. 8 kJ.

Option B. 4 kJ.

Option C. 2 kJ.

Correct Answer is. 4 kJ.

Explanation. Kinetic energy = 1/2mV. Only the V is squared. 2 metric tonnes = 2000 kg.

Question Number. 7. The work done in lifting a mass of 2000 kg vertically to a height of 40 metres is.

Option A. 80 kJ.

Option B. 784.8 kJ.

Option C. 500 kJ.

Correct Answer is. 784.8 kJ.

Explanation. Work done = Force * distance (force = mass * gravity). Wd = 2000 * 10 * 40 = 800,000 approx. (answer is slightly less because g = 9.81, not 10).

Question Number. 8. If a machine has a mechanical advantage of 10 and a velocity ratio of 20. The efficiency of the machine is.

Option A. 200%.

Option B. 0.5.

Option C. 2.

Correct Answer is. 0.5.

Explanation. 10 times the force out and only 1/20th speed, it must have an efficiency of a 1/2. (100% efficient it would have 10 times the force and 1/10th the speed - straight trade of force for speed).

Question Number. 9. 1 Watt =.

Option A. 1kg/h.

Option B. 1 Joule/s.

Option C. 1 HP.

Correct Answer is. 1 Joule/s.

Explanation. 1 Watt = 1 Joule/second.

Question Number. 10. How would you work out the work done by a machine assuming it is 100% efficient?.

Option A. Input and output.

Option B. Mechanical advantage and output.

Option C. Mechanical advantage and input.

Correct Answer is. Mechanical advantage and input.

Explanation. Assuming the 'input' means input force, to calculate the work done you will need the input force and the mechanical advantage of the machine to calculate the output force and distance (Work done = force * distance of output).

Question Number. 11. Ignoring friction, if you let an object slide down a slope, at the bottom.

Option A. the potential energy is equal to the kinetic energy.

Option B. the potential energy is more than the kinetic energy.

Option C. the kinetic energy is more than the potential energy.

Correct Answer is. the kinetic energy is more than the potential energy.

Explanation. All potential energy is converted to kinetic energy.

Question Number. 12. 1 HP = 33000 ft.lbs/min or 500 ft.lbs/s or.

Option A. 736 Watts.

Option B. 746 Watts.

Option C. 1360 Watts.

Correct Answer is. 746 Watts.

Explanation. 1 HP = 746 Watts.

Question Number. 13. A force of 15N is needed to move a body of mass 30kg along a footpath with uniform velocity. Find the coefficient of dynamic friction.(take g as 10m/s/s).

Option A. 1/20.

Option B. 1/2.

Option C. 20.

Correct Answer is. 1/20.

Explanation. NIL.

Question Number. 14. A mass of 400kg moves 27 metres with a force of 54N. What is the work produced?.

Option A. 10.1kJ.

Option B. 583.2kJ.

Option C. 1458J.

Correct Answer is. 1458J.

Explanation. NIL.

Question Number. 15. The SI unit of Power is the.

Option A. Volt.

Option B. Pascal.

Option C. Watt.

Correct Answer is. Watt.

Explanation. NIL.

Question Number. 16. What is 1 joule in calories?.

Option A. 4.186.

Option B. 252.

Option C. 0.239.

Correct Answer is. 0.239.

Explanation. NIL.

Question Number. 17. If you push an object with a force of 5 N for 10 m in 4 seconds, how much power is used?.

Option A. 12.5 watts.

Option B. 8 watts.

Option C. 200 Watts.

Correct Answer is. 12.5 watts.

Explanation. NIL.

Question Number. 18. What is the Kinetic Energy of a 2 kg object moving at a velocity of 12 m/s?.

Option A. 24 Joules.

Option B. 288 Joules.

Option C. 144 Joules.

Correct Answer is. 144 Joules.

Explanation. NIL.

Question Number. 19. A mass of 3kg weighs approximately.

Option A. 0.675 N.

Option B. 6.6 LB.

Option C. 1.3 LB.

Correct Answer is. 6.6 LB.

Explanation. 1 kg = 2.2 lb. So 3 kg = 3 * 2.2 = 6.6 lb.

Question Number. 20. Power is the rate of doing work. It is measured in.

Option A. Watts/Seconds.

Option B. Joules/Seconds.

Option C. Joules * Seconds.

Correct Answer is. Joules/Seconds.

Explanation. NIL.

Question Number. 21. A 6000 kg engine is lifted off a wing to a height 0.5 metres and then pushed across the hangar 24 meters. The force required to push the trolley is 12 kN. What is the work done to move the trolley?.

Option A. 298kJ.

Option B. 84MJ.

Option C. 288kJ.

Correct Answer is. 288kJ.

Explanation. NIL.

Question Number. 22. A ball is dropped from rest. What is its speed after 4 seconds? (Take g as 10m/s/s).

Option A. 80m/s.

Option B. 40m/s.

Option C. 20m/s.

Correct Answer is. 40m/s.

Explanation. NIL.

Question Number. 23. 1 KW is equal to.

Option A. 1.34 HP.

Option B. 1000 Joules.

Option C. 252 BTU.

Correct Answer is. 1.34 HP.

Explanation. NIL.

Question Number. 24. Ten kilograms is expressed numerically as.

Option A. 1 Mg.

Option B. 10 K.

Option C. 10 kg.

Correct Answer is. 10 kg.

Explanation. 10 kilograms = 10 kg.

Question Number. 25. An object accelerating down a slope would gain kinetic energy.

Option A. less than the potential energy lost.

Option B. greater than the potential energy lost.

Option C. equal to the potential energy lost.

Correct Answer is. equal to the potential energy lost.

Explanation. NIL.

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