英语翻译1.Can the speed of an object change if the net work done on it is zero?2.Discuss whether any work is being done by each of the following agents and,if so,whether the work is positive or negative.a.a chicken scratching the groundb.a person

英语翻译1.Can the speed of an object change if the net work done on it is zero?2.Discuss whether any work is being done by each of the following agents and,if so,whether the work is positive or negative.a.a chicken scratching the groundb.a person
英语翻译
1.Can the speed of an object change if the net work done on it is zero?
2.Discuss whether any work is being done by each of the following agents and,if so,whether the work is positive or negative.
a.a chicken scratching the ground
b.a person reading a sign
c.a crane lifting a bucket of concrete
d.the force of gravity on the bucket in (c)
3.Furniture movers wish to load a truck using a ramp from the ground to the rear of the truck.One of the movers claims that less work would be required if the ramp’s length were increased,reducing its angle with the horizontal.Is this claim valid?Explain.
4.A pendulum swings back and forth,as shown at right.Does the tension force in the string do work on the pendulum bob?Does the force of gravity do work on the bob?Explainyour answers.
5.The drivers of two identical cars heading toward each other apply the brakes at the same instant.The skid marks of one of the cars are twice as long as the skid marks of the other vehicle.Assuming that the brakes of both cars apply the same force,what conclusions can you draw about the motion of the cars?
6.When a punter kicks a football,is he doing work on the ball while his toe is in contact with it?Is he
doing work on the ball after the ball loses contact with his toe?Are any forces doing work on the ball
while the ball is in flight
7.A person lifts a 4.5 kg cement block a vertical distance of 1.2 m and then carries the block horizontally a distance of 7.3 m.Determine the work done by the person and by the force of gravity in this process.
8.A plane designed for vertical takeoff has a mass of 8.0 × 103 kg.Find the net work done by all forces on the plane as it accelerates upward at 1.0 m/s2 through a distance of 30.0 m after starting from rest.

英语翻译1.Can the speed of an object change if the net work done on it is zero?2.Discuss whether any work is being done by each of the following agents and,if so,whether the work is positive or negative.a.a chicken scratching the groundb.a person
1、一个物体,当它所受到的各种力的功为0时,它的速度是否会改变?
2、下面各种情况中,介质是否做功?如果做功,那么此功为正还是为负?
A、小鸡抓挠地面
B、人阅读信号/记号
C、吊车吊起一桶混凝土
D、作用于桶身上的重力
3、一辆货车利用它后面的活动梯/斜坡木（货车自带的,那种斜坡或者2根木板,用来形成一个坡度）来把家具装运进货车李；当斜坡木长度增加,和地面的水平角度变小的时候,在装运过程中有一个动作所做功会减小,这种说法是否正确?解释为什么.
4、一个钟摆前后摆动,运行良好.在这个过程中,连接钟锤的绳子是否对种锤做功?重力是否对种锤做功?解释原因.
5、两辆完全一样的车,相向驶来,两车的司机同时刹车；一辆车的刹车痕的长度是另一辆车的刹车痕的2倍,假设这两辆车刹车时所受到的摩擦力大小完全一样,那么关于这两辆车的运动,你能得到什么结论?
6、一个赌球的人踢球,当他的脚趾正接触在球的时候,此时他在做功吗?当他的脚趾正好离开球的时候,此时他在做功吗?球飞出去的时候,此时是否有力在做功?
7.一个人垂直抬起了一个质量为4.5千克的水泥块,垂直抬起距离为1.2米,然后又水平移动了7.3米,问在这个过程中这个人做了多少功,重力又做了多少功?
8.一团东西,在一个星球上垂直方向所受到的重力为8.0 X 103千克.问这团东西,从静止的状态起,以1.0米/平方秒的加速度向上抬起30米距离,各种力所做的功分别是多少.