UC知道一些物理题~~~在线等~~~帮我帮我啊~~
来源：百度知道 编辑：UC知道 时间：2024/05/07 05:23:14
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It is not uncommon during the service of a professional tennis player for the racket to exert an average force, F, of 157.0 N on the ball. If the ball has a mass of 0.065 kg and is in contact with the strings of the racket for 0.030 s, what is the kinetic energy of the ball as it leaves the racket? Assume that the ball starts from rest. Assume that air resistance is negligible.
为了球拍能施加平均力量， F， 157.0 N在球在一个职业网球球员的服务期间是不不凡的。 如果球有0.065公斤并且接触球拍时间为0.030 s，球的动能是多少？假设球从停止开始。 假设没有空气阻力
A 4.0 kg block is pushed 2.6 m at a constant speed up a vertical wall by a constant force applied at an angle of 30.0° with the horizontal
Assume that the coefficient of kinetic friction between the block and the wall is 0.30.
(a) Determine the work done by the force on the block.
(b) Determine the work done by gravity on the block.
(c) Determine the normal force between the block and the wall.
一个4千克的物体被竖直靠墙向上用恒定的速度推了2。6米，该力的方向是东偏北3
It is not uncommon during the service of a professional tennis player for the racket to exert an average force, F, of 157.0 N on the ball. If the ball has a mass of 0.065 kg and is in contact with the strings of the racket for 0.030 s, what is the kinetic energy of the ball as it leaves the racket? Assume that the ball starts from rest. Assume that air resistance is negligible.
为了球拍能施加平均力量， F， 157.0 N在球在一个职业网球球员的服务期间是不不凡的。 如果球有0.065公斤并且接触球拍时间为0.030 s，球的动能是多少？假设球从停止开始。 假设没有空气阻力
球的动能W=1/2mv^2
v=at
a=F/m=157N/0.065kg=2415m/s^2
v=2415m/s^2*0.03s=72.5m/s
球的动能W=1/2mv^2=1/2*0.065kg*(72.5m/s)^2=171J
A 4.0 kg block is pushed 2.6 m at a constant speed up a vertical wall by a constant force applied at an angle of 30.0° with the horizontal
Assume that the coefficient of kinetic friction between the block and the wall is 0.30.
(a) Determine the work done by the force on the block.
(b) Determine the work done by gravity on th