13. A 45 kg swimmer starting from rest can develop a maximum speed of 12 m/s over a distance of 20 m. How much net force must be applied to do this? 14. A net force of 3000 N is accelerating a 1200 kg elevator upward. If the elevator starts from rest, how long will it take to travel up 15 m? 15. A 57 kg paratrooper falls through the air. How much force is pulling him down? 16. A net force of 34 N is applied to accelerate an object at a rate of 2.5 m/s². What is the mass of the object? 17. A runner exerts a net force of 225 N to accelerate at a rate of 3.0 m/s². What is the runner's mass? 18. What average net force is required to stop a 4 kg bowling ball in 0.5 s if it's initially traveling at 10 m/s? 19. A hockey puck with a mass of 0.18 kg is at rest on the horizontal frictionless surface of the rink. A player applies a horizontal force of 0.5 N to the puck. Find the speed and the traveled distance 5 s later.
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Step 1: Calculate the acceleration of the swimmer using the equation \(a = \frac{v_f^2 - v_i^2}{2d}\), where \(v_f = 12 \, m/s\), \(v_i = 0 \, m/s\), and \(d = 20 \, m\). Show more…
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12. Until the time of Galileo and Newton, people believed that a constant force is required to produce a constant speed. Do your observations confirm or reject this notion? 13. What happens to the speed as you proceed farther and farther along the measured distance? 14. What happens to the rate of increase in speed – the acceleration – as you proceed farther and farther along the measured distance? 15. When the force is the same, how does the acceleration depend upon the mass? 16. When the mass of the skater is the same, how does the acceleration depend upon the force?
Umar Sohail Q.
In Fig. 4.15 an astronaut is playing shuffleboard on Earth. The puck has a mass of $2.0 \mathrm{kg} .$ Between the board and puck the coefficient of static friction is 0.35 and that of kinetic friction is $0.25 .$ (a) If she pushes the puck with a force of $5.0 \mathrm{N}$ in the forward direction, does the puck move? (b) As she is pushing, she trips and the force in the forward direction suddenly becomes $7.5 \mathrm{N} .$ Does the puck move? (c) If so, what is the acceleration of the puck along the board if she maintains contact between puck and stick as she regains her footing while pushing steadily with a force of $6.0 \mathrm{N}$ on the puck? (d) She carries her game to the Moon and again pushes a moving puck with a force of $6.0 \mathrm{N}$ forward. Is the acceleration of the puck during contact more, the same, or less than on Earth? Explain.
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