A 15.0 g rubber bullet hits a wall with a speed of 140 m/s. If the bullet bounces straight back with a speed of 125 m/s, what is the change in momentum of the bullet?
To determine the change in momentum of the bullet, we need to calculate the initial momentum and the final momentum, and then find the difference between them.
The momentum of an object is defined as the product of its mass and velocity. Mathematically, momentum (p) can be expressed as:
p = m * v
where:
p is momentum,
m is mass, and
v is velocity.
Given data:
Mass of the bullet (m) = 15.0 g = 0.015 kg
Initial velocity of the bullet (v1) = 140 m/s
Final velocity of the bullet (v2) = -125 m/s (since it bounces back)
Step 1: Calculate the initial momentum.
p1 = m * v1
Substituting the given values:
p1 = 0.015 kg * 140 m/s
p1 = 2.1 kg*m/s
Step 2: Calculate the final momentum.
p2 = m * v2
Substituting the given values:
p2 = 0.015 kg * (-125 m/s)
p2 = -1.875 kg*m/s (negative sign indicates the opposite direction of motion)
Step 3: Calculate the change in momentum.
Change in momentum (Δp) = p2 - p1
Substituting the values we calculated earlier:
Δp = (-1.875 kg*m/s) - (2.1 kg*m/s)
Δp = -4.975 kg*m/s
Therefore, the change in momentum of the bullet is approximately -4.975 kg*m/s.