大师作文网一道英文物理题关于圆周运动
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一道英文物理题关于圆周运动
A massless rigid rod of length L = 36.7 cm has a ball of mass m = 0.074 kg attached to one end.The other end is pivoted so that the ball moves in a vertical circle.The ball is launched from the horizontal position A with an initial downward speed v0.It just reaches point D and stops.
Calculate v0.
What is the tension in the rod at B?
Some grit is placed on the pivot,creating a frictional force.The ball now just reaches C when launched from A with the same speed as before.Calculate the mechanical energy dissipated by friction during this motion.
A massless rigid rod of length L = 36.7 cm has a ball of mass m = 0.074 kg attached to one end.The other end is pivoted so that the ball moves in a vertical circle.The ball is launched from the horizontal position A with an initial downward speed v0.It just reaches point D and stops.
Calculate v0.
What is the tension in the rod at B?
Some grit is placed on the pivot,creating a frictional force.The ball now just reaches C when launched from A with the same speed as before.Calculate the mechanical energy dissipated by friction during this motion.
长度为L=36.7厘米一个无质量刚性杆有一质量为m球=0.074公斤一端连接.另一端枢转,以使球在竖直圆移动.球从水平位置A推出具有初始向下速度v 0.恰好到达D点出停止.
1.计算V0.
2.计算B点出杆的弹力
若有摩擦力的时候,从A以相同的速度释放,小球恰好能达到C,计算运动过程中摩擦消耗的机械能.
由机械能守恒得,以A点处为零势面
0+1/2m(V0)^2=mgL+0
V0=根号下2gL≈2.7m/s
由机械能守恒得,以A点处为零势面
0+1/2m(V0)^2=-mgL+1/2m(VB)^2
m(VB)^2=4mgL
由牛顿第二定律得
T-mg=[m(VB)^2]/L
T=5mg=3.7N
分析能量转化
重力在此运动过程中做的总功为0
∴1/2m(V0)^2=Wf
Wf=0.26973J≈0.3J
1.计算V0.
2.计算B点出杆的弹力
若有摩擦力的时候,从A以相同的速度释放,小球恰好能达到C,计算运动过程中摩擦消耗的机械能.
由机械能守恒得,以A点处为零势面
0+1/2m(V0)^2=mgL+0
V0=根号下2gL≈2.7m/s
由机械能守恒得,以A点处为零势面
0+1/2m(V0)^2=-mgL+1/2m(VB)^2
m(VB)^2=4mgL
由牛顿第二定律得
T-mg=[m(VB)^2]/L
T=5mg=3.7N
分析能量转化
重力在此运动过程中做的总功为0
∴1/2m(V0)^2=Wf
Wf=0.26973J≈0.3J