Force is defined as mass times acceleration. Starting with SI base units, derive a unit for force. Using SI prefixes, suggest a convenient unit for the force resulting from a collision with a 10-ton trailer truck moving at 55 mi per hour and for the force resulting from the collision of a molecule of mass around 10 - 20 kg moving almost at the speed of light (3 * 108 m/s) with the wall of its container. (Assume a 1-second deceleration time for both collisions.)

12–13. Tests reveal that a normal driver takes about 0.75 s before he or she can react to a situation to avoid a collision. It takes about 3 s for a driver having 0.1% alcohol in his system to do the same. If such drivers are traveling on a straight road at 30 mph (44 ft/s) and their cars can decelerate at 2 ft/s², determine the shortest stopping distance d for each from the moment they see the pedestrians. Moral: If you must drink, please don't drive! vq = 44 ft/s Prob. 12–13

Large birds like pheasants often walk short distances. Small birds like chickadees never walk. They either hop or fly. Why might this be?

1) A train is travelling at 60km/h when Superman slams head-on into it bringing it smoothly to a stop before it falls off a cliff. Superman is able to stop the train in an amazing 2.5 seconds! what is the acceleration of the train? how many g's did the people on the train pull during this stop? (hint: 1g = 9.8m/s^2) 2)you are about to skateboard down a long hill. Your initial velocity is 2.0 m/s south. When you reach the bottom of the hill you are travelling at 6.0 m/s south. It took 57 seconds to reach the bottom of the hill. What was your displacement?

The 25-Mg boxcar A 16m/s to the right is coasting on the horizontal track when it encounters a 9-Mg car B coasting at 2m/s toward it. If the two cars meet and couple together, determin common speed in m/s just after the coupling. Please see details below. Rounding numbers to 2 decimal places at the end.

According to Guinness, the tallest man to have ever lived was Robert Pershing Wadlow of Alton, Illinois. He was last measured in 1940 to be 2.72 meters tall (8 feet, 11 inches). Determine the speed which a quarter would have reached before contact with the ground if dropped from rest from the top of his head.

(27) A 55 kg woman is seated in the passenger seat of a car traveling at a velocity of 15.0 m/s. In an emergency, the car is brought to a stop in 0.50 seconds. What force does the seatbelt exert on the woman so that she remains in her seat and accelerates (slows down) with the car?

A car weighing 2.5 metric tons and traveling at 90 km/h hits a 500 m long stretch of black ice. Unfortunately, due to skidding, neither accelerating nor braking has any effect on the speed! The driver manages to maintain steady straight direction of motion and the only impact is provided by the ice friction force, which is numerically equal to 4v² Newtons, where the velocity v of the car is measured in m/sec. (a) Using Newton's Second Law F = ma, set up a mathematical model for the position x(t) and velocity v(t) of the car as functions of time t. Start by drawing a diagram and choosing a consistent system of units based on kg, m, sec (1 ton = 1000 kg, 1 m/sec = 3.6 km/h, 1 N = 1 kg · m/sec²). Introduce and label the variables, show the units and write down the differential equations and the intial conditions. (b) Use the model in part a to calculate v(t) and x(t). Fully show the process of solving the initial value problems. (c) Based on your work so far, how long will it take to pass…

A woman of 67 kg is held firmly in her seat by her seatbelt during a collision. The car deccelerates from 55km/h to 0.00km/h in 0.14s. Calculate the force of the seatbelt on the woman: