牛顿运动定律

两位站着不动的胖子和瘦子，为什么把胖子撞倒会比把瘦子撞倒困难？

Two fat and thin men standing still, why is it more difficult to knock a fat man than a thin man?

• 因为撞胖子时会产生较强的反作用力

  Because it will produce a strong reaction force when knocking fat man

• 因为胖子的质量大，因此他的惯性也大

  Because the fat man's mass is large, his inertia is also large

• 因为撞胖子的需要做更多的功

  Because it takes more work to knock fat man

• 因为撞胖子时动量变化率小

  Because the rate of change of momentum when knocking fat man is small

吊着货物的起重机，当货物________________时，起重机纲缆的张力是最大的。

When the cargo is crane, the tension of the crane cable is the largest when the cargo is ________________.

• 停在空中不动

  stationary

• 等速下降

  moving down with uniform speed

• 加速下降

  moving down with acceleration

• 减速下降

  moving down with deceleration

在没有外力的情况下，物体总是保持静止或匀速直线运动。

In the absence of external force, the object always remains stationary or moves at constant speed in a straight line.

• 牛顿第一运动定律

  Newton's 1st Law

• 牛顿第二运动定律

  Newton's 2nd Law

• 牛顿第三运动定律

  Newton's 3rd Law

• 牛顿万有引力定律

  Newton's Gravitational Law

作用在物体的合力为零，物体可能

When the resultant force acting on a body is zero. The body may

I. 静止 Stay at rest

II. 匀速运动 Moving with constant speed

III. 匀加速运动 Moving with constant acceleration

• I

• II

• I, II

• I, III

可尼可以在_____体验失重的情况

Cony can experience the feel of loss of weight in a ____

I. 匀加速向上运动的升降机

Lift moving upward with uniform acceleration

II. 匀加速向下运动的升降机

Lift moving downward with uniform acceleration

III. 匀减速向上运动的升降机

Lift moving upward with uniform deceleration

IV. 匀减速向下运动的升降机

Lift moving downward with uniform deceleration

• I, II

• II, III

• III, IV

• I, IV

在 F 的作用下，两物体做匀加速运动，求 T

Both objects move with constant acceleration under F, determine T

• $\frac{4F}{3}$

• $\frac{3F}{4}$

• $\frac{F}{3}$

• $\frac{F}{4}$

求 determine  $F_{XY}$  

•  $\frac{4F}{3}$  

•  $\frac{3F}{4}$  

•  $\frac{F}{4}$  

•  $\frac{F}{3}$  

下列哪对属于作用力反作用力？

Which of following refers to action reaction pair?

• 桌子上书的重力和桌子对书的支持力

  Weight of book and normal reaction force on book

• 吊灯对天花板的拉力和天花板对灯的拉力

  Pull of chandelier to ceiling and pull of ceiling to chandelier

• 汽车前进的牵引力和地面对车的摩擦力

  Driving force on car and friction on car

• 火箭的推动力和火箭的重力

  thrust on rocket and weight of rocket

图示质量为1.5 kg物体的 F-t 图象,最初处于静止状态。求5s后的速度
F-t graph for a 1.5 kg body which initially at rest. Determine the velocity after 5 s.

• 20 m/s

• 10 m/s

• 4 m/s

• 3 m/s

求两个物体的加速度

Determine the acceleration for both object

• 7 m s^-2

• 4.2 m s^-2

• 9.8 m s^-2

• 3 m s^-2