Question

A professional boxer hits his opponent with a 1000-N horizontal blow that lasts for 0.150 s. (a) Calculate the impulse imparted by this blow. (b) What is the opponent’s final velocity, if his mass is 105 kg and he is motionless in midair when struck near his center of mass? (c) Calculate the recoil velocity of the opponent’s 10.0-kg head if hit in this manner, assuming the head does not initially transfer significant momentum to the boxer’s body. (d) Discuss the implications of your answers for parts (b) and (c).

Answer 1

Answers:

a. 150 kg m/s

b. 1.43 m/s

c. 15 m/s

d. It will be easier to knock someone out if the boxer hits the opponent's head than if he hits the body.

Step-by-step explanation:

Part (a)

The impulse is equal to the net force multiply by time, so the impulse imparted by this blow will be equal to:

Part (b)

Additionally, the impulse is also equal to the change in momentum, so:

`J=\Delta p=m(v_f-v_i)`

Where m is the mass, vf is the final velocity and vi is the initial velocity.

Now, we can replace the impulse by 150 kg m/s, the mass by 105 kg, and the initial velocity by 0 m/s:

Solving for vf, we get:

So, when struck near his center of mass the final velocity will be 1.43 m/s

Part(c)

If the boxer hits his opponent in the head, we only need to take into account the mass of the head, so we can calculate the final velocity in the same way of part (b) as follows:

So, in this case, the final velocity will be 15 m/s

Part (d)

Since 15 m/s is greater than 1.43 m/s will be easier to knock someone out if the boxer hits the opponent's head than if he hits the body.