Jan and len throw identical rocks off a tall building at the same time. the ground near the building is flat. jan throws her rock straight downward. len throws his rock downward and outward such that the angle between the initial velocity of the rock and the horizon is 30°. len throws the rock with a speed twice that of jan's rock. if air resistance is negligible, which rock hits the ground first?

rock will hit the ground at the same time.

Explanation:

given,

Jan throws rock vertically downward with some initial velocity(v).

Len throw rock at an angle of 30° with initial velocity(2 v) twice than the Jan

to find whose rock will hit the ground first.

it is given that rock is identical

now,            

vertical component of velocity of the rock

  = v₂ sin θ

  = v₂ sin 30°

 =

 = v

hence the vertical velocity of the Len is same as that of Jan so the rock will hit the ground at the same time.

the small 0.38-kg slider is known to move from position a to position b along the vertical-plane slot. determine (a) the work done on the body by its weight and (b) the work done on the body by the spring. the distance r = 0.70 m, the spring modulus k = 154 n/m, and the unstretched length of the spring is 0.53 m

explanation:

-reverse card

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.