Question

A rifle can shoot a 4.20-g bullet at a speed of 965 m/s.a)Find the KE of the bullet at this speed.b) What work is done on the bullet if it starts from rest?c) If thework is done over a distance of 0.75 m, what is the average force on the bullet?d) If the bullet comes to rest by pushing 1.5 cm into metal, what is the magnitude and direction of the average force the metal exerts?

Answer 1

Answer:

a)  1955.6 J

b) 1955.6 J

c) 2607 N

d) 110373 J

Explanation:

a) $Kinetic\ Energy = \frac{1}{2} mv^2 = \frac{1}{2} \times \frac{4.2}{1000} \times 965^2 = 1955.6 J$

b) Work done on bullet should be increase in KE = 1955.6 J

c) Work done = Force \times displacement = KE of bullet

              $F = \frac{1955.6}{0.75} = 2607 N$

d) Work done to stop $= KE = F_{stop} \times d_{stop}$

$F_{stop} = \frac{1955.6}{\frac{1.5}{100}} = 110373 J$