Direction of the torque –out off the plane

spin

somersault

Chapters 6 & 7, example #2

A car of mass 800 kg, moving at a speed of 50 m/s, runs into the rear end of a car of mass 1000 kg in front, which moves in the same direction at a speed of 40 m/s. If the first car slows down to a speed of 40 m/s, what is the speed of the second car immediately after the impact, assuming it keeps moving forward in the same direction? What is the total KE of these two cars before the collision? How much KE is lost due to the collision? If, instead, the two cars get stuck together after the collision, what would be their speed immediately after the impact and the KE loss? Ans: 48 m/sec, 1.8 x 106 J, 8 x 103 J, 44.4 m/s,

and 2.2 x 104 J Chapter 7, example #2

A 100 N force is applied to push down the end of the longer arm of a lever by a distance of 0.8 m while the load is lifted up by a height of 0.2 m. What is the mass of the load? What is the ratio in length of the two lever arms? Ans: m = 40 kg and L/l = 4. Chapter 8, example #1 A person, standing still at the edge of a rotating platform with an angular speed of 20 RPM, is moving at a speed (tangential) of 4 m/s. What is the radius of the platform? What would be the tangential speed of the person if he/she moves to halfway between the rotational axis and the outer edge of the platform? Ans: 1.91 m and 2 m/s.