After the player kicks the football out, the work done by the football in the air is (air resistance is not included) a. How does kick work on the ball b. Gravity does work on the ball c. There is no force to work on the ball d. Not sure

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• 1. When the ball with a mass of 1kg is released freely from 3m, the resistance of the ball is 0.1 times of the gravity The ball with a mass of 1kg is released freely from 3m. The resistance of the ball in motion is 0.1 times that of gravity. Assuming that the ball does not lose mechanical energy when colliding with the ground, the path of the ball from the beginning to the final rest is determined
• 2. On a smooth horizontal plane, there is a uniform thin plate with a mass of 4kg, which moves at a uniform speed of 3m / s. A 1kg ball falls into point a 20 m above the plate and rebounds to 5M high. The collision lasts for a very short time, and the gravitational impulse can be ignored 1. The elastic impulse of the plate to the ball during the collision 2. The dynamic friction coefficient between the plate and the ball is 0.08, and the velocity and direction of the plate after collision are calculated Does the ball have a horizontal speed after touch? If so, send it out 3. When the ball falls back on the board again, the distance between the ball's landing point on the board and a
• 3. There is a steel plate placed horizontally on the ground. There is a steel ball with mass m = 1kg at 3M above it. It moves vertically downward at the initial velocity V0 = 2m / s. assuming that the ball is subject to a constant air resistance f = 2n, there is no kinetic energy loss when the ball collides with the steel plate, and the ball finally stops moving (1) What's the speed of the first bounce? (2) The height of the first bounce? (3) What's the distance s it takes to stop?
• 4. At a height of 45m from the ground, a small ball with a mass of 0.1kg starts to fall freely. The instantaneous power of gravity at the end of the first second? The average power of gravity work in the second second second?
• 5. The ball with mass of M = 1kg rolls down from point a at the upper end of 1 / 4 smooth circular arc groove with radius r of 1, and leaves the circular arc horizontally at point B at the height h = 3M above the ground (1) The velocity VA when leaving the circular groove (2) Landing speed VC size (3) The work done by gravity throughout the process
• 6. A basketball with a gravity of 5N is thrown vertically. It is assumed that the resistance of air to the basketball is 0.5N, Then the resultant forces of the basketball in the process of vertical rising and falling are (10N / kg) A.5.5N,5N B.5.5N,4.5N C.4.5N,5.5N D.5N,4.5N
• 7. If the ratio of the initial velocity to the velocity back to the throwing point is k, and the air resistance is constant during the motion, the ratio of gravity to resistance is K______ ．
• 8. When a charged ball moves from point m to point n in the air, it is respectively affected by gravity, air resistance and electric field force. In the process of movement, the electric field force does 14J work on the ball, the ball overcomes the air resistance and does 4J work, and the kinetic energy of the ball increases 8j A. The gravitational potential energy of the ball at M is more than that at N 2 & nbsp; JB. The mechanical energy of the ball at M is more than that at n 4 & nbsp; JC. The mechanical energy of the ball at M is 10 & nbsp; more than that at n JD. The electric potential energy of the ball at M is 14 & nbsp; more than that at n J
• 9. When an object moves in the air along the vertical direction, and only under the action of gravity and air resistance, the motion of the object will be stable（ When an object moves in the air along the vertical direction, and only under the action of gravity and air resistance, the () a potential energy, B kinetic energy, C mechanical energy and d mechanical energy of the object may not be changed
• 10. A small ball is thrown vertically at the initial velocity of 21 M / s. suppose that the air resistance of the ball is 0.05 times of the gravity, then the maximum height of the ball is______ m. The speed of falling back to the throw point is_____ M / S (g = 10) m/s2).
• 11. I found this, ∵ 1pA * 1m & # 179; = 1n / m2 * 1m & # 179; = 1n · M = 1J work = pressure * volume
• 12. When a 1n heavy object is lifted 1m high, the work done by the force on the object must be equal to 1J This sentence is wrong. Why?
• 13. Is the work done to overcome gravity by an object with a weight of 1n, which is accelerated vertically or raised 1m vertically at a uniform speed, 1J? Is work done by overcoming gravity the work done by gravity?
• 14. The object with weight of 1n is increased by 1m under the action of vertical tensile force. Why is the work done by tensile force not 1J
• 15. Lift an object with a gravity of 1n by 1m, do work by 1J, do work by gravity by 1J, and the gravitational field sucks the object past If you lift an object with a gravity of 1n by 1m and do work of 1J, the gravitational field will absorb the object. However, if you want to separate the object, you also need to do work. What is the total energy of the universe Is it conservation? I don't know whether to fill in a specific number, anyway, the topic is like this
• 16. Does gravity work on a football when it's flying in the air? Be accurate!
• 17. There is an apple of 2n weight. By gravity and air resistance, we can calculate the resultant force F1 and F2 when it rises and falls in the process of throwing upward Why F1 = G + F resistance? F2 = G-F resistance?
• 18. An apple with a mass of 0.2kg is thrown up vertically, and the air resistance in the process of rising and falling is 1n
• 19. Draw a graph of the gravity of the object below. G = 10 N / kg (1) a small ball with a mass of 8 kg when it falls freely in the air (excluding air resistance)
• 20. When an apple is thrown up, it is subjected to gravity and air resistance The resultant force of apple in the process of rising -- the resultant force of apple in the process of falling