Hold a pencil in front of your eye at a position where its blunt end just blocks out the moon. make appropriate measurements to estimate the diameter of the moon, given that the earth–moon distance is 3.8 × 105 km. assume that the pencil has a diameter of about 0.7 cm, and it just blocks out the moon if it is held about 0.75 m from the eye. express your answer using two significant figures.

One hazard of space travel is debris left by previous missions. there are several thousand masses large enough to detect by radar orbiting the earth, but there are far greater numbers of very small masses such as flakes of paint. calculate the force exerted by a 0.110 mg chip of paint that strikes a space shuttle window at a relative speed of 5.00 ✕ 103 m/s and sticks, given the collision lasts 6.00 ✕ 10-8 s. such a collision chipped the window of the ill-fated challenger in june 1983, causing $50,000 of damage.