A780g, 50-cm-long metal rod is free to rotate about a frictionless axle at one end. while at rest, the rod is given a short but sharp 1000n hammer blow at the center of the rod, aimed in a direction that causes the rod to rotate on the axle. the blow lasts a mere 2.5ms.

what is the rod's angular velocity immediately after the blow? the book gives the answer 8.0rad/s

9.6 rad/s

Explanation:

= length of the metal rod = 50 cm = 0.50 m

= Mass of the long metal rod = 780 g = 0.780 kg

Moment of inertia of the rod about one end is given as

= force applied by the hammer blow = 1000 N

Torque produced due to the hammer blow is given as

= time of blow = 2.5 ms = 0.0025 s

= Angular velocity after the blow

Using Impulse-change in angular momentum, we have

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.