In a ballistics test, a 28-g bullet pierces a sand bag that is 30 cm thick. If t
ID: 1287002 • Letter: I
Question
In a ballistics test, a 28-g bullet pierces a sand bag that is 30 cm thick. If the initial bullet velocity was 55 m/s and it emerged from the sand bag moving at 18 m/s, what was the magnitude friction force (assuming it to be constant) that the bullet experienced while it traveled through the bag?Showing work In a ballistics test, a 28-g bullet pierces a sand bag that is 30 cm thick. If the initial bullet velocity was 55 m/s and it emerged from the sand bag moving at 18 m/s, what was the magnitude friction force (assuming it to be constant) that the bullet experienced while it traveled through the bag?
Showing work
Showing work
Explanation / Answer
Here is the progress so far (without the numbers).
We assume the thickness is x and the velocities are u1=55m/s and u2=18m/s, mass is m=28*10-3
Initial energy = (1/2)*m*u12=(1/2)*28*10-3*552=42.35J
Final energy = (1/2)*m*u22 = (1/2)*28*10-3*182=4,536J
The work of friction is negative and it's equal to:
W=T*x=?E (final energy - initial energy) <=> T*0,3=42.35-4,536 <=> T=37.814/0,3=126N? What did I do wrong? Can you check it a bit?