大学物理双语练习题

Chapter 1 Particle Kinematics

I) Choose one correct answer among following choices

1. An object is moving along the x-axis with position as a function of time given by

x=x(t). Point O is at x=0. The object is definitely moving toward O when

2. An object starts from rest at x=0 when t=0. The object moves in the x direction with positive velocity after t=0. The instantaneous velocity and average velocity are related by

A. v v

B. v v

C. v v

dx x can be larger than, smaller than, or equal to

3. An object is moving in the x direction with velocity

A. Negative.

B. Zero.

C. Positive.

D. Not determined from the information given. 4. An object is moving on the xy-plane with position as a function of time given by r = 2 2 a t i + b t j (a and b are constant). Which is correct?

A. The object is moving along a straight line with constant speed.

B. The object is moving along a straight line with variable speed.

C. The object is moving along a curved path with constant speed.

D. The object is moving along a curved path with variable speed.

5. An object is thrown into the air with an initial velocity v 0 (4.9i 9.8 j)m/s.

Ignore the

air resistance (空气阻力 ). At the highest point the magnitude of the velocity

is ( )

(A) 0 (B) 4.9m/s (C) 9.8m/s (D) (4.9)2 (9.8) 2 m/s

6. Two bodies are falling with negligible air resistance, side by side, above a horizontal

plane. If one of the bodies is given an additional horizontal acceleration during its descent, it A. dx 0 dt B. dx 0 dt C. d(x 2) dt D. d(x 2) dt

D.

v x (t), and x is nonzero x dt

constant. With v x 0 when t=0, then for t>0 the quantity v x dv x v x

dt is

A.strikes the plane at the same time as the other body.

B.strikes the plane earlier than the other body.

C.has the vertical component of its velocity altered.

D.has the vertical component of its acceleration altered.

7. A toy racing car moves with constant speed around the circle shown below. When it is at point A its coordinates are x=0, y=3m and its velocity is 6m/s i . When it is at

point B its velocity and acceleration are:

22

A.-6m/s j and 12m/s i , respectively.

B. 6m/s j and -12m/s i , respectively.

22

C. 6m/s j and 12m/s i , respectively.

D. 6m/s j and 2m/s i , respectively.

8. A stone is tied to a 0.50-m string and whirled at a constant speed of 4.0m/s in a vertical circle. Its acceleration at the bottom of the circle is:

2 2 2 2

A. 9.8m/s , up

B. 9.8m/s , down

C. 8.0m/s , up

D. 32m/s , up

9. A boat is able to move through still water at 20m/s. It makes a round trip to a town

3.0 km upstream. If the river flows at 5m/s, the time required for this round trip is:

B.150 s

C. 200 s

D. 320 s

A. 120 s

II)Fill in the empty space with correct answer

1. A particle goes from x=-2m, y=3m, z=1m to x=3m, y=-1m, z=4m. Its displacement is : .

2.The x-component of the position vector of a particle is shown in the graph in Figure

as a function of time.

(a)The velocity component v x at the instant 3.0 s is .

(b)When is the velocity component zero ? The time is .

(c)Is the particle always moving in the same direction along the x-

axis? .

2

3.The angle turned through by a wheel is given byθ ＝at+bt , where a and b are constants. Its angular velocityω ＝, and its angular accelerationβ ＝

4.When a radio wave impinges on the antenna of your car, electrons in the antenna

move back and forth along the antenna with a velocity

component v x as shown schematically in Figure . Roughly sketch

the same graph and indicate the time instants when

(a)The velocity component v x is zero;

(b)The acceleration componenta x is zero;

(c)The acceleration has its maximum magnitude.

5. A car is traveling around a banked, circular curve of radius 150 m on a test track. At the instant when t=0s, the car is moving north, and its speed is 30.0 m/s but decreasing uniformly, so that after 5.0 s its angular speed will be 3/4 that it was when t=0s. The angular speed of the car when t=0s is , the angular speed 5.0 s later

is , the magnitude of the centripetal acceleration of the car when t=0s is , the magnitude of