Charlotte, a 60.0-kg skin diver, shoots a 2.0-kg spear with a speed of 15 m/s at a fish who darts quickly away without getting hit. How fast does Charlotte move backwards when the spear is shot? (Hint: To start, Charlotte and the spear are together and both are at rest)

Charlotte move backwards with 0.5 m/s when the spear is shot

Explanation:

Before collision;

m₁ = 60 kg

m₂ = 2 kg

v = 0 (since, Charlotte and the spear are together and both are at rest)

After collision

m₁ = 60 kg

m₂ = 2kg

v₁ = ?

v₂ = 15 m/s

From principle of conservation of linear moment, total momentum before collision must be equal to total momentum after collision.

v(m₁ + m₂) = m₁v₁ + m₂v₂

0 (60+2) = 60v₁ + 2 x 15

0 = 60v₁ + 30

60v₁ = -30

v₁ = - 30/60

v₁ = - 0.5 m/s

Therefore, Charlotte move backwards with 0.5 m/s when the spear is shot.

0.5 m/s

Explanation:

From Newton's third law of motion,

Total momentum before collision = Total momentum after collision

mu+m'u' = mv+m'v' Equation 1

Where m = mass of the Charlotte, m' = mass of the spear, u = initial velocity of the Charlotte, u' = initial velocity of the spear, v = Final velocity of the Charlotte, v' = Final velocity of the  spear.

Note: Since the Charlotte and the spear where initially at rest,

0 = mv+m'v'

-mv = m'v'

make v the subject of the equation

v = -(m'v'/m) Equation 2

Given: m = 60 kg, m' = 2.0 kg, v' = 15 m/s

Substitute into equation 2

v = -(2×15/60)

v = -0.5 m/s.

The negative sign shows that the Charlotte moves backward, which is in opposite direction to the motion of the spear

answer: b.

explanation:

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.