Sagot :

miss32

Réponse:

ex 8

Ec ( en J) = 1/2 x m ( en kg ) x v² ( en m/s) = 1/2 x 45 x 12000/3600 = 75 J

ex 9

Ec = 1/2 x 1000 × 100000/3600 = 13 888 J

Explications:

1km = 1000m

donc 12 km = 12000m

1h = 3600 s

1 tonne = 1000 kg