Question

Mass of bullet 0.8 kg is fired with the velocity of 80m/s.Calculate its kinetic energy.​

Answer 1

Answer:

Mass of bullet, m=100g=

1000

100

​

kg=

10

1

​

kg

Velocity of bullet, v=100ms

−1

Mass of gun, M=20kg

Let recoil velocity of gun =V

Before firing, the system (gun+bullet) is at rest, therefore, initial momentum of the system =0

Final momentum of the system = momentum of bullet + momentum of gun

=mv+MV=

10

1

​

×100+20V=10+20V

Applying law of conservation of momentum, Final momentum = Initial momentum

i.e., 10+20V=0

20V=−10

or V=−

20

10

​

=−0.5ms

−1

.

Negative sign shows that the direction of recoil velocity of the gun is opposite to the direction of the velocity of the bullet.

Explanation:

Answer 2

Answer:

A bullet of mass 0.8kg is fired with a velocity of 80m/s, the kinetic energy of the bullet is 2560J

Explanation:

• Kinetic energy is the energy of a moving body

• for a body of mass (m) moving with velocity (v) kinetic energy is given by the formula

               $KE=\frac{1}{2} mv^{2}$

From the question, it is given that

mass of the bullet $m=0.8kg$

the velocity of the bullet $v=80m/s$

therefore kinetic energy of the bullet,

$KE=\frac{1}{2}*0.8*80*80=2560J$