Concept explainers
(a)
The impulse athlete receives from the platform.
(a)
Answer to Problem 20P
The impulse athlete receives from the platform is
Explanation of Solution
Impulse experienced by the athlete is caculated from expression of impulse force law .
Write the expression for the impulse force law.
Here ,
Conclusion:
Substitute
Thus, the impulse athlete receives from the platform is
(b)
The velocity with which it reaches the platform.
(b)
Answer to Problem 20P
The velocity with which it reaches the platform is
Explanation of Solution
The athlete jumps on a plateform this converts potential energy to kinetic energy.
Write the expression for the conservation of energy.
Here
Write the expression for the initial kinetic energy.
Here,
Initially athlete jumps from the rest so initial velocity is zero.
Substitute
Write the expression for the initial potential energy.
Here,
Write the expression for the final kinetic energy.
Here,
Write the expression for the final potential energy.
Here,
Substitute
Substitute
Conclusion:
Substitute
Thus, the velocity with which it reaches the platform is
(c)
The velocity with which athlete leaves the platform.
(c)
Answer to Problem 20P
The velocity with which athlete leaves the platform is
Explanation of Solution
The athlete falls on the platform as a result impulse is produced.
Write the expression for the net impulse.
Here,
Write the expression for the impulse due to gravity.
Here,
Write the expression for the impulse momentum law.
Here,
Write the expression for the change in momentum.
Here,
Write the expression for the initial momentum.
Write the expression for the final momentum.
Substitute
Substitute
Substitute
Simplify the above equation for
Conclusion:
Substitute
Thus, the velocity with which athlete leaves the platform is
(d)
The height athlete jumps from the platform.
(d)
Answer to Problem 20P
The height athletes jumps from platform is
Explanation of Solution
The athlete jumps from the plateform to some height. Hence, kinetic energy is converted to gain potential energy.
Write the expression for the conservation of energy.
Here,
Write the expression for the initial kinetic energy at plateform .
Here,
Initially athlete jumps from the rest so initial velocity is zero.
Write the expression for the initial potential energy on platform.
Here,
Initial height at plateform is zero.
Substitute
Write the expression for the final kinetic energy at max height.
Here,
Substitute
Write the expression for the final potential energy at max height.
Here
Substitute
Simplify the above expression for value of
Conclusion:
Substitute
Thus, the height athletes jumps from platform is
Want to see more full solutions like this?
Chapter 9 Solutions
Physics for Scientists and Engineers With Modern Physics
- A particle moves in a medium under the influence of a retarding force equal to mk(υ3+ a2υ), where k and a are constants. Show that for any value of the initial speed the particle will never move a distance greater than π/2kaand that the particle comes to rest only for t → ∞.arrow_forwardWhether or not an object (such as a plate, glass, or bone) breaks upon impact depends on the average force exerted on that object by the surface. When a 1.2-kg glass figure hits the floor, it will break if it experiences an average force of 330 N. When it hits a tile floor, the glass comes to a stop in 0.015 s. From what minimum height must the glass fall to experience sufficient force to break? How would your answer change if the figure were falling to a padded or carpeted surface? Explain.arrow_forwardA high jumper with a body weight of 820 N exerts an average vertical force of 1640 N down on the floor for 0.75 s. The average vertical force exerted on the jumper by the floor is:arrow_forward
- A 2.8 kg ball strikes a wall with a velocity of 6.7 m/s to the left. The ball bounces off with a velocity of 5.0 m/s to the right. If the ball is in contact with the wall for 0.38 s, what is the constant force exerted on the ball by the wall? Answer in units of N.arrow_forwardTwo blocks with mass m1 = 1 kg, and m2 = 2 kg start from rest. The same force, F, acts on both of them. If the applied force is applied to each of them over equal times, t. Find the ratio of their final kinetic energies (KE1 / KE2)arrow_forwardWhether or not an object (such as a plate, glass, or bone) breaks upon impact depends on the average force exerted on that object by the surface. When a 2.5 kg glass figure hits the floor, it will break if it experiences an average force of 538 N. When it hits a tile floor, the glass comes to a stop in 0.020 s. From what minimum height (in m) must the glass fall to experience sufficient force to break? m How would your answer change if the figure were falling to a padded or carpeted surface? Explain. The duration of the collision would be shorter, so the average force for a given change in momentum would be more.The duration of the collision would be longer, so the average force for a given change in momentum would be less. The duration of the collision would be longer, so the average force for a given change in momentum would be more.The duration of the collision would be shorter, so the average force for a given change in momentum would be less.arrow_forward
- A chandelier of mass 18kg hangs from a cable that is attached to a ceiling. The chandelier is at rest and initially the cable hangs vertically.Alice climbs up the stairs to a height level that is close to the chandelier's height. She then pulls the chandelier to one side using a hook, to bring the chandelier closer to her so she can replace a light bulb. The force that Alice exerts on the chandelier is in the horizontal direction and has magnitude 42 N.arrow_forwardStarting from rest, a 57.0 kg woman jumps down to the floor from a height of 0.800 m, and immediately jumps back up into the air. While she is in contact with the ground during the time interval 0 < t < 0.800 s, the force she exerts on the floor can be modeled using the functionarrow_forwardEmma 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?arrow_forward
- Physics students do an expriment to determine the coefficient of kinetic friction between a wooden object and the horizontal table it is on. This object has a mass of 1.6 kg. The students push it against a spring, which compresses the spring by 18cm. When released, the spring sends the object moving across the table and it stops 82 cm from where it was released. The spring constant is 200 N/m. Find the obeject-table coefficient of kinetic friction.arrow_forwardYou wake up one morning to find yourself in a strange room with opaque walls, and no visible doors or windows. You decide to do some experiments to find out more about your strange situation. Your own body mass is 53.3 kg. You pick up an object and drop it from rest, starting at a height of 2.40 meters above the floor, and it hits the floor 0.560 seconds later. You can ignore air resistance. Based on the outcome of this experiment, when you step on the scale provided for you, what weight will it register for your body? 544 N 816 N 522.9 N 408 Narrow_forwardA man pushing a crate of mass m = 92.0 kg at a speed of v = 0.870 m/s encounters a rough horizontal surface of length = 0.65 m as in the figure below. If the coefficient of kinetic friction between the crate and rough surface is 0.360 and he exerts a constant horizontal force of 285 N on the crate. (a) Find the magnitude and direction of the net force on the crate while it is on the rough surface. magnitude direction ---Select--- (b) Find the net work done on the crate while it is on the rough surface. (c) Find the speed of the crate when it reaches the end of the rough surface. m/sarrow_forward
- Physics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningClassical Dynamics of Particles and SystemsPhysicsISBN:9780534408961Author:Stephen T. Thornton, Jerry B. MarionPublisher:Cengage Learning