Lub zog - cov teeb meem thiab cov kev daws teeb meem

Power is the rate at which work is done in a given period. Mathematically, power is the work/time ratio.

P = W/t

Description: P = power (Joule/second = Watt), W = work (Joule), t = time interval (second)

Based on this equation, it can be concluded that the greater the work rate, the greater the power. On the other hand, the smaller the work rate, the smaller the power. Work rate refers to the rate at which work is done.

Power is a scalar. The SI unit of power is the Joule/second. The Joule/second = Watt (abbreviated as W), named so to pay homage to James Watt. The British imperial unit for power is foot-pound per second.

This unit is too small for practical purposes, so the greater unit horsepower (abbreviated as hp) is used. One horsepower = 550 foot-pound per second = 764 Watt = ¾ kilowatt.

The amount of work can also be expressed in power x time units, for instance, kilowatt-hour or kWh. One kWh refers to the work done at a constant rate of 1 kiloWatt for one hour.

1. Ib qho 50-kg person runs up the stairs 10 meters high in 2 feeb. Acceleration vim gravity (g) is 10 m/s². Txiav txim lub hwj chim.

Paub:

Pawg (m) = 50 kg

Qhov siab (h) = 10 meters

Acceleration vim lub ntiajteb txawj nqus (g) = 10 m/s²

Lub sijhawm luv (t) = 2 feeb = 2 (60) = 120 thib obs

xav : hwj chim (P)

Tshuaj:

Formula of power :

P = W / t

P = hwj chim, W = ua hauj lwm, t = lub sij hawm

Formula of Work :

W = F s = w h = m g h

W = ua hauj lwm, F = quab yuam, wb = hnyav, d = xaav, h = qhov siab, m = mass, g = acceleration vim lub ntiajteb txawj nqus

W = m g h = (50)(10)(10) = 5000 Joule.

P = W / t = 5000 / 120 = 41.7 Joule/second.

2. Calculate the power required of a 60-kg person who climbs a tree 5 meters high in 10 seconds. Acceleration due to gravity is 10 m/s².

Paub:

Qhov hnyav (m) = 60 kg

Qhov siab (h) = 5 meterss

Acceleration vim lub ntiajteb txawj nqus (g) = 10 m/s²

Lub sijhawm luv (t) = 10 vib nas this

xav : hwj chim

Tshuaj:

Ua Haujlwm:

W = m g h = (60)(10)(5) = 3000 Joule

Lub hwj chim:

P = W / t = 3000 / 10 = 300 Joule/second.

3. A rotary comedy with a power of 300 watts and period of 5 minutes rotates 5 rounds. The energy it uses is ….

A. 15 kJ

B. 75 kJ

C. 90 kJ

D. 450 kJ

Paub:

Lub zog (P) = 300 Watts = 300 Joules/ob

Period (T) = 5 minutes = 5 (60 seconds) = 300 seconds

Number of rotation = 5

SE pob: Energy used by the rotary comedy

Tshuaj:

Cov lus teb yog D.

[wpdm_package id='1190′]

1. Work was done by force problems and solutions
2. Cov teeb meem thiab kev daws teeb meem ntawm lub zog ua haujlwm-kinetic
3. Cov teeb meem thiab kev daws teeb meem ntawm lub hauv paus ntsiab lus ntawm lub zog ua haujlwm-mechanical
4. Cov teeb meem thiab kev daws teeb meem ntawm lub zog gravitational
5. Lub zog muaj peev xwm ntawm cov teeb meem caij nplooj ntoos hlav elastic thiab kev daws teeb meem
6. Teeb meem fais fab thiab kev daws teeb meem
7. Kev siv ntawm kev txuag lub zog mechanical rau kev txav mus los dawb
8. Kev siv ntawm kev txuag lub zog kho tshuab rau kev txav mus rau saum thiab nqis hauv kev txav mus los dawb
9. Kev siv ntawm kev txuag lub zog kho tshuab rau kev txav mus los ntawm qhov chaw nkhaus
10. Kev siv ntawm kev txuag lub zog kho tshuab rau kev txav mus los ntawm lub dav hlau inclined
11. Kev siv ntawm kev txuag lub zog kho tshuab rau kev txav mus los ntawm projectile