What features should you look for in a crash helmet, and why?

During a discus throw, Arthur's arm rotates 25 rad/s, and the discus is 1.5 m from the axis of rotation when he releases it. Blake's arm rotates 30 rad/s, and the discus is 1.1 m from the axis of rotation when he releases it.

A 9.0 g wad of sticky clay is hurled horizontally at a 90 g wooden block initially at rest on a horizontal surface. The clay sticks to the block. After impact, the block slides 7.50 m before coming to rest.

If you precisely measure the position of a particle, you A. destroy its wave nature. B. cause it to diffract. C. destroy all information about its speed or momentum. D. cause the particle to be annihilated.

What happens when the molecules in a steel bar absorb energy, and start moving quickly?

Which of these is most likely to be attracted to a magnet? A. a book B. staple C. stone D. eraser

A geologist estimates that a large boulder weighs 7840 N. What should he estimate the mass of this boulder to be? A. 650 kg B. 740 kg C. 780 kg D. 800 kg

Two objects have the same momentum. Do the velocities of these objects necessarily have (a) the same directions and (b) the same magnitudes? Give your reasoning in each case.

If you keep voltage constant and increase resistance resistance, what happens to current?

A scene in a movie has a stuntman falling through a floor onto a bed in the room below. The plan is to have the actor fall on his back, but a researcher has been hired to investigate the safety of this stunt.

During energy transformation, all energy systems: are a. 100 percent efficient b. lose energy c. gain heat energy d. create energy