What force does a trampoline have to apply to Jennifer, a 45.0-kg gymnast, to accelerate her straight up at 7.50 m/s² ? The answer is independent of the velocity of the gymnast-she can be moving up or down or can be instantly stationary.

On an essentially frictionless, horizontal ice rink, a skater moving at 4.0 m/s encounters a rough patch that reduces her speed by 44% due to a friction force that is 28% of her weight.

Emma and Katie are racing along in their new wagon. Upon reaching the bottom of the hill traveling at 13.2 m/s, Katie notices her teddy bear 12.0 m in front of them, panics and locks the brakes sending the wagon into a skid. If the wagon and its contents have a total mass of 1.50 x10^1 kg, and the coefficient of kinetic friction between the road and the rubber wagon tires is (0.75), by how much does the wagon miss the bear?

As a protest against the umpire's calls, a baseball pitcher throws a ball straight up into the air at a speed of 22.0 m/s. In the process, he moves his hand through a distance of 1.20 m. If the ball has a mass of 0.150 kg, find the force he exerts on the ball to give it this upward speed.

A boy of mass m = 36 kg is standing initially at rest relative to the moving walkway, which has a constant horizontal speed u = 1.1 m/s. He decides to accelerate his progress and starts to walk from point A with a steadily increasing speed and reaches point B (a distance s = 29 m) with a speed dx/dt = v = 2.5 m/s relative to the walkway. During his acceleration he generates an average horizontal force F between his shoes and the walkway. Calculate the work done on the boy by the force F from an absolute viewpoint and then from a relative viewpoint. Explain the difference. Answers: Absolute viewpoint, Work = i Relative viewpoint, Work = i J

The high-speed winds around a tornado can drive projectiles into trees, building walls, and even metal traffic signs. In a laboratory simulation, a standard wood toothpick was shot by pneumatic gun into an oak branch. The toothpick mass was 0.15 g, its speed before entering the branch was 212 m/s, and its penetration depth was 17 mm. If its speed was decreased at a uniform rate, what was the magnitude of the force of the branch on the toothpick? Number Units

In the movie The Rocketeer, a teenager discovers a jet-powered backpack in an old barn. The backpack allows him to fly at incredible speeds. In one scene, however, he uses the backpack to rapidly accelerate an old pickup truck that is being chased by “bad guys.” He does this by bracing his arms against the cab of the pickup and firing the backpack, giving the truck the acceleration of a drag racer. Is the physics of this scene “Good,”“Bad,” or “Ugly?” Draw and Explain.