Chapter 1 Particle Kinematics
I) Choo one correct answer among following choices
水晶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
A. B. C. D.
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. B. C.
D. can be larger than, smaller than, or equal to
3. An object is moving in the x direction with velocity , and is nonzero constant. With when t=0, then for t>0 the quantity is
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 = a t2 i+ b t2 j (a and 胡子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 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) 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. 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 . When it is at point B its velocity and acceleration are:
A. -6m/sand 12m/s2, respectively. B. 6m/s and -12m/s2 , respectively.
C. 6m/sand 12m/s2, respectively. D. 6m/s and 2m/s2 , respectively.
太平洋地震带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:
A. 9.8m/s2, up B. 9.8m/s2, down C. 8.0m/s2, up D. 32m/s2, 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:
A. 120 s B. 150 s C. 200 s D. 320 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 vx at the instant 3.0 s is 过秦论译文 .
(b) When is the velocity component zero ? T党的发展历程he time is .
(c) Is the particle always moving in the same direction along the x-axis? .
3. The angle turned through by a wheel is given by θ＝at+bt2, where a and b are constants. Its angular velocity ω＝ , and围棋技巧 its angular acceleration β＝ .
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 vx as shown schematically in Figure . Roughly sketch the same graph and indicate the time instants when
(a) The velocity component vx is zero;
(b) The acceleration component ax is zero;
(c) The acceleration has its maximum magnitude.
《为学》原文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 林徽因情诗 , the magnitude of the centripetal acceleration of the car when t=5.00s is , the magnitude of the angular acceleration is , the magnitude of the tangential acceleration is .
