One horsepower is approximately equal to
- A.100 watt
- B.500 watt
- C.746 watt
- D.1000 watt
Correct answer
Explanation
The correct answer is C, 746 watt. The horsepower is an older unit of power that survives in the rating of motors and vehicles, and one horsepower is taken as about 746 watt, that is roughly three quarters of a kilowatt.
Option A, 100 watt, is close to the rating of an old filament bulb and has no connection with the horsepower. Option B, 500 watt, is simply half a kilowatt and is offered as a plausible round figure. Option D, 1000 watt, is one kilowatt; a common mistake is to treat the horsepower and the kilowatt as equal, when in fact one kilowatt is about 1.34 horsepower. The figure 746 is worth memorising exactly, because the question is often set in reverse, asking how many watt a motor of a given horsepower consumes.
Read the full article: Work, Energy and Power: Formulas, Units and Conversions
Practice Questions
View allWhat is the SI unit of work?
- A.Newton
- B.Joule
- C.Watt
- D.Pascal
Show answer
Work is the product of force and displacement, so its unit is the newton metre, which is given the name joule; one joule of work is done when a force of one newton moves a body through one metre in its own direction.
Read the full explanation →The work done by a force is zero when the angle between the force and the displacement is
- A.0 degrees
- B.45 degrees
- C.90 degrees
- D.180 degrees
Show answer
Work equals force into displacement into the cosine of the angle between them, and the cosine of ninety degrees is zero, so a force at right angles to the motion does no work at all.
Read the full explanation →The kinetic energy of a body of mass m moving with speed v is given by
- A.mass into g into height
- B.half of mass into the square of the speed
- C.mass into the speed
- D.mass into the square of the speed
Show answer
Kinetic energy is the energy a body has because of its motion, and it grows with the square of the speed, so a body moving twice as fast carries four times the kinetic energy.
Read the full explanation →What is the SI unit of power?
- A.Joule
- B.Watt
- C.Newton second
- D.Kilowatt hour
Show answer
Power is the rate of doing work, that is work divided by the time taken, so its unit is the joule per second, which is named the watt after James Watt.
Read the full explanation →The commercial unit of electrical energy is the
- A.Joule
- B.Watt
- C.Kilowatt hour
- D.Erg
Show answer
Household electricity is billed in these units, and one kilowatt hour, popularly called one unit, is the energy consumed when an appliance of one kilowatt runs for one hour; in SI terms it equals 3.6 million joule.
Read the full explanation →