11. Momentum & Impulse

A 300g bullet is fired horizontally into a 10-kg wooden block initially at rest on a horizontal surface. The coefficient of kinetic friction between block and surface is 0.6. The bullet remains embedded in the block, which then slides 35 m along the surface before stopping. What was the initial speed of the bullet?

In a physics lab, a cube slides down a frictionless incline as shown in Fig. 9–57 and elastically strikes another cube at the bottom that is only one-half its mass. If the incline is 45 cm high and the table is 95 cm off the floor, where does each cube land? [Hint: Both leave the incline moving horizontally.]

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Astronomers estimate that a 2.0-km-diameter asteroid collides with the Earth once every million years. The collision could pose a threat to life on Earth.

(a) Assume a spherical asteroid has a mass of 3200 kg for each cubic meter of volume and moves toward the Earth at 15 km/s. How much destructive energy could be released when it embeds itself in the Earth?

A “doomsday” asteroid with a mass of 2.0 x 10¹⁰ kg is hurtling through space. Unless the asteroid’s speed is changed by about 0.20cm/s , it will collide with Earth and cause tremendous damage. Researchers suggest that a small “space tug” sent to the asteroid’s surface could exert a gentle constant force of 2.5 N. For how long must this force act?