Nā nīnau hoʻohālike e pili ana i ka Ikehu Mekanika

6 mau laʻana o nā nīnau ikehu mīkini

ʻO ke kumumanaʻo hana-ikehu mīkini

1. E hoʻolohe i ke kiʻi ka neʻe ʻana poloka penei! Manaʻo ʻo g = 10 m/s²Inā ʻo ke koina o ka friction kinetic ma waena o ka poloka a me ka papahele μk = 0,5, a laila ʻo ka waiwai o ka neʻe ʻana o ka mea (s) he ….

A. 5,00 m

B. 4,25 m

C. 3,00 m

D. 2,50 m

E. 2,00 m

Pahana

Ua ʻike ʻia :

Ka helu o ka haʻalulu kinetic (μk) = 0,5

Ka nuipa o ka poloka (m) = 4 kg

Ka wikiwiki ma muli o ke koʻikoʻi (g) = 10 m/s²

Kaumaha o ka poloka (w) = mg = (4)(10) = 40 Newton

Inā aia ka poloka ma luna o kahi pālahalaha, a laila ʻo ka ikaika maʻamau (N) = kaumaha (w) = 40 Newtons.

Ka wikiwiki mua (v₁) = 5 m/s

Ka wikiwiki hope loa (v₂) = 0 m/s

Ua nīnau ʻia : ka neʻe ʻana o ka (mau) mea?

Pane :

ʻŌlelo ke kumumanaʻo ikehu hana-mekanika ua like ka hana (W) i hana ʻia e kahi ikaika non-conservative me ka loli o ka ikehu mechanical o ka mea a i ʻole ka ikehu mechanical hope loa (EM).₂) – ikehu mīkini mua (EM)₁). He ikaika mālama ʻole ka friction kinetic a ʻo ka ikaika mālama ʻole wale nō e hana ana ma ka poloka ʻo ia ka friction kinetic.

W= ΔEM

f_k s = EM₂ – EM₁

Nā hana i hana ʻia e ka friction kinetic:

W = f_k s = (μk)(N)(s) = (0,5)(40)(s) = 20 kekona

Nā loli i ka ikehu mechanical:

ΔEM = EM₂ – EM₁ = (EK + EP)₂ – (EK + EP)₁

Neʻe nā mea ma luna o kahi pālahalaha a ʻaʻole ʻike i nā loli o ke kiʻekiʻe (Δh = 0) no laila ʻaʻohe loli o ka ikehu hiki ke hoʻonui ʻia ka umekaumaha (ΔEP = EP₂ – EP₁ = 0). No laila, ʻo ka loli o ka ikehu mechanical e pili wale ana i ka loli o ka ikehu kinetic.

ΔEM = EK₂ – EK₁ = ½ mv₂² – ½ mv₁² = ½ m (v₂² - v₁²)

ΔEM = ½ (4)(0² - 5²) = (2)(25) = 50

ʻO ka neʻe ʻana o ka poloka:

W= ΔEM

20 kekona = 50

s = 50 / 20 = 2,5 mika

ʻO D ka pane pololei.

Ke kānāwai o ka mālama ʻana i ka ikehu mechanical

2. He like ke kaumaha o nā mea A a me B. Hāʻule ka mea A mai ke kiʻekiʻe o h mika a hāʻule ʻo B mai 2h mika. Inā paʻi ʻo A i ka honua me ka wikiwiki o vm/s, a laila e paʻi ka mea B i ka honua me ka ikehu kinetic o….

A. 2 mv²

B. mv²

C. 3/4 mv²

D. 1/2 mv²

E. 1/4 mv²

Pahana

ʻO ka wikiwiki hope loa o ka mea B e hāʻule kūʻokoʻa ana mai ke kiʻekiʻe o 2h penei:

v² = 2 g (2h) = 4 gh

ʻO ka ikehu kinetic o ka mea B:

EK_B = ½ mv² = ½ m (4 gh) = 2 mgh —– Kaulike 1

ʻO ka ikehu mechanical mua o ka mea B ka ikehu hiki ke umekaumaha = mg h. ʻO ka ikehu mechanical hope loa o ka mea B ka ikehu kinetic = ½ mv².

Ke kānāwai o ka mālama ʻana i ka ikehu mechanical :

mgh = ½ mv².

Kārena mgh = ½ mv² a laila hiki iā mākou ke pani iā ​​mgh ma ka hoohalike 1 me ½ mv².

Ikehu kinetic o ka mea B = 2 mgh = 2(½ mv²) = mv²

ʻO ka pane pololei ʻo B.

3. E nānā i ke kiʻi ma lalo! Hāʻule kūʻokoʻa kekahi mea mai ke kiʻekiʻe o 20 m. Inā he 10 m/s ka wikiwiki ma muli o ke koʻikoʻi, a laila ʻo ka wikiwiki o ka mea i kona wā he 15 m ma luna o ka honua he….

A. 2 m/s

B. 5 m/s

C. 10 m/s

D. 15 m/s

E. 20 m/s

Pahana

Ikehu mīkini hope loa = ikehu mīkini mua

ʻO ka ikehu kinetic o ka mea ma ke kiko 2 = ka emi ʻana o ka ikehu hiki ke hoʻopaʻa ʻia e 5 mika

½ mv² = mgh

½ v² = (10)(20-15)

½ v² = (10)(5)

½ v² = 50

v² = (2)(50)

v² = 100

v = 10 m/s

ʻO C ka pane pololei.

4. Ua paʻa kahi poloka ma ka piko o kahi mokulele hilig e like me ka mea i hōʻike ʻia ma ke kiʻi. Ke hoʻokuʻu ʻia, paheʻe ka poloka me ka ʻole o ka friction ma ke ala piʻi. ʻO ka wikiwiki o ka poloka ke hiki i ka lalo o ke ala piʻi he…

A. 6 ms^-1

B. 8 ms^-1

C. 10 ms^-1

D. 12 ms^-1

E. 16 ms^-1

Pahana

Ikehu mechanical mua = ikehu hiki ke hoʻopaʻa ʻia ka umekaumaha = mgh = m (10)(5) = 50 m

Ikehu mīkini hope loa = ikehu kinetic = 1/2 mv²

ʻŌlelo ke kānāwai o ka mālama ʻana i ka ikehu mechanical ʻo ka ikehu mechanical mua = ka ikehu mechanical hope loa.

EM_o = EM_t

50 m = 1/2 mv²

50 = 1/2 v²

2 (50) = v²

100 = v²

v = 10 m/s

ʻO C ka pane pololei.

5. Ua hoʻokuʻu ʻia kahi poloka me ke kaumaha o m kg mai ke kiʻekiʻe o h mika ma luna o ka honua e like me ka mea i hōʻike ʻia ma ke kiʻi. ʻO ka lakio o ka ikehu hiki (EP) a me ka ikehu kinetic (EK) ke aia ma ke kiko M ʻo….

A. 1 : 3

B. 1 : 2

K. 2 : 1

D. 2 : 5

E. 3 : 7

Pahana

Ikehu hiki ke hoʻopaʻa ʻia ma ke kiko M:

EP_M = mg (0,3 h)

Ikehu kinetic ma ke kiko M = ka emi ʻana o ka ikehu hiki ke hoʻopaʻa ʻia e h-0,3h = 0,7 h

EK_M = EP = mg (0,7 h)

ʻO ka lakio o ka ikehu hiki ke hoʻopaʻa ʻia e ka umekaumaha a me ka ikehu kinetic ma kahi M:

EP_M : EK_M

mg (0,3 hola) : mg (0,7 hola)

0,3: 0,7

3: 7

ʻO ka pane pololei ʻo E.

6. E nānā i ke kiʻi o ka mea A e hāʻule wale ana mai ke kiko P ma lalo!

Inā ʻo EP_Q a me EK_Q ʻo kēlā me kēia ka ikehu hiki a me ka ikehu kinetic ma ke kiko Q (g = 10 m/s²), a laila EP_Q : EK_Q ʻo ia….

A. 16 : 9

B. 9 : 16

K. 3 : 2

D. 2 : 3

E. 2 : 1

Pahana

Ikehu hiki ke hoʻouluulu ʻia ma ke kiko Q:

EP_Q = mgh = (m)(10)(1,8) = 18 m

Ikehu kinetic ma ke kiko Q = ka emi ʻana o ka ikehu hiki ke hoʻopaʻa ʻia e 5-1,8 = 3,2 mika

EK_Q = EP = mgh = m (10)(3,2) = 32 m

ʻO ka lakio o ka ikehu hiki ke hoʻopaʻa ʻia e ka umekaumaha a me ka ikehu kinetic ma kahi Q penei:

EP_Q : EK_Q

18 mika: 32 mika

18: 32

9: 16

Puna nīnau:

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