物理位置與運動 DSE、CE 選擇題

1.

Mary walks along a triangular path $XYZ$ where $XY = YZ = ZX$ . It takes her $10$ s, $20$ s and $10$ s to travel through $XY$ , $YZ$ and $ZX$ respectively. Which of the following graphs best represents the variation of distance travelled with time ?

2.

A car is travelling at a constant speed of $50$ km h $^{-1}$ . How much time does it take to travel $500$ m ?

3.

The figure above shows three paths $P_1$ , $P_2$ and $P_3$ from $X$ to $Y$ on a horizontal plane. Three students take the same time to travel from $X$ to $Y$ via the three paths respectively. Which of the following physical quantities about their journey is/are the same ?

(1)displacement

(2)distance

(3)average speed

4.

John and Mary are driving two cars, $P$ and $Q$ , along a straight horizontal road respectively. At time $t = 0$ , they both see an obstacle and apply the brakes to stop the cars with uniform deceleration. The variation of velocity with time of the two cars is shown in the figure below. Which of the following statements is/are correct ?

(1)The two cars have the same initial speeds.

(2)The reaction times of John and Mary are the same.

(3)The total stopping distances of the two cars are the same.

Velocity-time graphs of P (higher initial speed) and Q, both constant for the same reaction time then decreasing linearly to zero at the same time

5.

A diver jumps up vertically in the air from a high platform and falls into water. The $v$ - $t$ graph below shows the variation of the velocity of the diver against time from the point he jumps ( $P$ ) until he is at the lowest point ( $Q$ ) in the water.

Diver path from platform point P up and down to point Q in water (not to scale), and velocity-time graph: 3 m/s at t = 0, zero at 0.3 s, -13 m/s at 1.6 s, back to zero at 2 s

Which of the following is correct ?

	Total distance travelled from $P$ to $Q$	Height of the platform above water surface
	$8.9$ m	$8$ m
	$10.6$ m	$10$ m
	$11.5$ m	$8$ m
	$11.5$ m	$10.6$ m

6.

Velocity-time graphs of a car (straight line from the origin to 20 m/s at 20 s) and a truck (constant 10 m/s)

At $t = 0$ , a car and a truck are at the same point on a horizontal straight road. Their velocity - time graph is shown in the figure above. Which of the following statements is correct ?

7.

A bicycle finishes a $100$ -metre journey in $9.77$ s. Assume that the bicycle starts from rest and moves with a uniform acceleration. What is the acceleration of the bicycle throughout the journey ?

8.

Velocity-time graphs of cars A (steep then shallow, solid) and B (shallow then steep, dashed) meeting at time T

Two cars $A$ and $B$ start from rest simultaneously and travel along the same straight road. The velocity-time graphs of the two cars are shown above. Which of the following statements about the motion of the two cars is/are always correct ?

(1)

A

and

B

have the same average velocity during the time interval

0

to

T

.

(2)

A

and

B

have the same average acceleration during the time interval

0

to

T

.

(3)

A

and

B

travel the same displacement during the time interval

0

to

T

.

9.

The acceleration of objects due to gravity on the Moon is about $1/6$ that on the Earth. Which of the following diagrams shows the correct velocity-time graphs for a free falling object dropping respectively on the Earth's surface and the Moon's surface ?

Four velocity-time diagrams A to D each showing lines for Earth and Moon

10.

A car travels along a straight road from $A$ to $B$ with a uniform acceleration. The speed of the car is $v_1$ at the instant when half of the journey time from $A$ to $B$ is elapsed and its speed is $v_2$ at the mid-way of $A$ and $B$ . Which of the following is correct ?