91影视

A typical atom has a diameter of about\({\bf{1}}{\bf{.0 \times 1}}{{\bf{0}}^{{\bf{ - 10}}}}\;{\bf{m}}\).

(a) What is this in inches?

(b) Approximately how many atoms are along a 1.0 cm line, assuming they just touch?

(I) How much work must be done to stop a 925-kg car traveling at 95 km/h?

Determine the conversion factor between (a) km/h and mi/h, (b) m/s and ft/s, and (c) km/h and m/s.

A 125-kg astronaut (including space suit) acquires a speed of \({\bf{2}}{\bf{.50}}\;{{\bf{m}} \mathord{\left/{\vphantom {{\bf{m}} {\bf{s}}}} \right.\\} {\bf{s}}}\) by pushing off with her legs from a 1900-kg space capsule.

(a) What is the change in speed of the space capsule?

(b) If the push lasts 0.600 s, what is the average force exerted by each on the other? As the reference frame, use the position of the capsule before the push. (c) What is the kinetic energy of each after the push?

(II) Two bullets are fired at the same time with the same kinetic energy. If one bullet has twice the mass of the other, which has the greater speed and by what factor? Which can do the most work?

A light-year is the distance light travels in one year (at speed = 2.998 脳 10⁸ m/s). (a) How many meters are there in 1.00 light-year? (b) An astronomical unit (AU) is the average distance from the sun to the earth, 1.50 脳 10⁸km. How many AU are there in 1.00 light-year?

(I) Three forces are applied to a tree sapling, as shown in Fig. 9鈥�46, to stabilize it. If\({\vec F_{\rm{A}}}=385\;{\rm{N}}\)and\({\vec F_{\rm{B}}} = 475\;{\rm{N}}\), find\({\vec F_{\rm{C}}}\)in magnitude and direction.

(II) A baseball (\(m = 145\;{\rm{g}}\)) traveling 32 m/s moves a fielder鈥檚 glove backward 25 cm when the ball is caught. What was the average force exerted by the ball on the glove?

How much longer (percentage) is a one-mile race than a 1500-mile race (鈥渢he metric mile鈥�)?

(II) A 2500-kg trailer is attached to a stationary truck at point B, Fig. 9鈥�61. Determine the normal force exerted by the road on the rear tires at A, and the vertical force exerted on the trailer by the support B.