(II) At an accident scene on a level road, investigators measure a car’s skid mark to be 78 m long. It was a rainy day and the coefficient of friction was estimated to be 0.30.
(c) What is wrong with a car that skids (see page 131)?

A 25-g projectile is fired into a cube of ballistic gel at a velocity of 360 m/s. If the projectile penetrates 15 cm into the gel before stopping, find the average force exerted by the gel onto the projectile. Use

(b) the work-energy principle.

(II) A car traveling at a velocity v can stop in a minimum distance d. What would be the car’s minimum stopping distance if it were traveling at a velocity of 2v?

(II) At an accident scene on a level road, investigators measure a car’s skid mark to be 78 m long. It was a rainy day and the coefficient of friction was estimated to be 0.30.

(a) Use these data to determine the speed of the car when the driver slammed on (and locked) the brakes.

(II) At an accident scene on a level road, investigators measure a car’s skid mark to be 78 m long. It was a rainy day and the coefficient of friction was estimated to be 0.30.

(b) Why does the car’s mass not matter?

II) A 1.60-m-tall person lifts a 1.65-kg book off the ground so it is 2.20 m above the ground. What is the potential energy of the book relative to

(c) How is the work done by the person related to the answers in parts (a) and (b)?

In the game of paintball, players use guns powered by pressurized gas to propel 33-g gel capsules filled with paint at the opposing team. Game rules dictate that a paintball cannot leave the barrel of a gun with a speed greater than 85 m/s. Model the shot by assuming the pressurized gas applies a constant force F to a 33-g capsule over the length of the 32-cm barrel. Determine F by

(a) using the work-energy principle, and

(II) A meteorite has a speed of 90.0 m/s when 750 km above the Earth. It is falling vertically (ignore air resistance) and strikes a bed of sand in which it is brought to rest in 3.25 m.

(b) How much work does the sand do to stop the meteorite (mass = 575 kg)?

(II) A NASA satellite is said to have observed an asteroid that is on a collision course with the Earth. The asteroid has an estimated mass, based on its size, of 4 x 10⁹ kg. It is approaching the Earth on a head-on course with a velocity of 600 m/s relative to the Earth and is now 5.0 x 10⁶ km away. With what speed will it hit the Earth’s surface, neglecting friction with the atmosphere?