Unit 2 Kinematics

Question 1

What is the definition of distance?

Answer 1

Distance, d, is the length of a path travelled by an object.

Question 2

What is the SI unit of distance?

Answer 2

The SI unit is the metre (m)

Question 3

What is the definition of displacement?

Answer 3

Displacement, s, is the distance in a specified direction from a reference point.

Question 4

What is the definition of speed?

Answer 4

Speed is the rate of change of distance travelled with respect to time.

Question 5

What is the SI unit of speed?

Answer 5

The SI unit is metre per second (m times s to the power of -1).

Question 6

The speed of an object may not remain uniform. True or false?

Answer 6

True.

Question 7

How do you find average speed?

Answer 7

Average speed is the total distance travelled by the object divided by the total time taken.

Question 8

How do you find the instantaneous speed?

Answer 8

Instantaneous speed is the rate of change of distance travelled at a particular instant.

Question 9

How can speed be expressed?

Answer 9

It can be expressed as
Speed = triangle d / triangle t

Where triangle d is the change in distance and triangle t is the change in time.

Question 10

What is velocity?

Answer 10

Velocity, v, is the rate of change of displacement with respect to time.

Question 11

What is the difference between speed and velocity?

Answer 11

Velocity, v, is the rate of change of displacement with respect to time while speed is the rate of change of distance travelled with respect to time.

Question 12

What is the SI unit of velocity?

Answer 12

The SI unit is metre per second (m s to the power of -1)

Question 13

How can velocity be expressed as?

Answer 13

v = triangle in s/ triangle in t

Where triangle s is the change in displacement and triangle t is the change in time.

Question 14

The velocity of an object during its motion may change. True or false.

Answer 14

True

Question 15

How can the average velocity be calculated?

Answer 15

Average velocity is the total change in displacement divided by the total time taken.

Question 16

How can the instantaneous velocity be calculated?

Answer 16

Instantaneous velocity is the rate of change of displacement at a particular instant.

Question 17

Griffles travelled a distance 10m to the right in the first 5.0 seconds at a uniform speed and then 10m to the left in the next 5.0 seconds at the same uniform speed. Calculate his total distance travelled, his displacement, his average speed and average velocity in the first 10 seconds.

Answer 17

Distance travelled:
10 m + 10 m =20 m

Displacement = 10 - 10 = 0m

Average speed and= 20m / 10s =2 m/s 2.0 m s to the power of -1 (2 s.f.)

Average velocity is= 0m/10s =0 m/s 0 ms to the power of -1.

Question 18

The railway line between two MRT stations is straight and horizontal. The distance between the two stations is 960m.
A train accelerates uniformly from rest as it leaves one station. After 16s, it reaches a speed of 20m/s. The train continues at this speed for a time t. The train then decelerates uniformly for 18 s and stops in the second station. What is the value of t?
A 14s
B 23s
C 31s
D 48s

Answer 18

By drawing the velocity time graph, you would be able to form an equation that equates to the total distance and find the value of t.

Question 19

A stone falling through the air has reached terminal velocity. Which row shows the acceleration and the velocity of the stone?

Options:
A zero (acceleration of the stone) constant (velocity of the stone)
B zero (acceleration of the stone) increasing (velocity of the stone)
C 10m/s square (acceleration of the stone) constant (velocity of the stone)
D 10m/s square (acceleration of the stone) increasing (velocity of the stone)

Answer 19

Ans: A

When the stone is at terminal velocity, this means that the stone has reached maximum velocity (the velocity does not change further and so, remains constant), hence the acceleration is 0.

Once an object reaches its terminal velocity, its velocity remains constant and hence its acceleration is 0.

Question 20

A train travels north at a velocity of 25m/s along a straight, horizontal track. At time t = 5.0s, its velocity starts to change and its acceleration is -2.0m/s square.
How is the train moving at time t = 15.0s?
A travelling north with decreasing speed
B travelling north with increasing speed
C travelling south with decreasing speed
D travelling south with increasing speed.

Answer 20

Ans: (A)

taking direction to the north as positive, difference in time, change in time = time (final) - time (initial) = 15.0-5.0 = 10.0s.

Given acceleration, a = -2.0m/s square (negative value, acting in opposite direction)<
change in velocity, change in velocity = acceleration times change in time = (-2.0)(10.0) = -20.0m/s

Final velocity, velocity (final_ = velocity initial + change in velocity = +25 + (-20.0) = +5.0m/s (velocity has decreased)

Since velocity (final)>0, the train is still travelling north.

Question 21

What is the no v formula?

Answer 21

s = ut + 1/2at square

Question 22

What is the no t formula?

Answer 22

v square = u square + 2as

Question 23

What is the no s formula?

Answer 23

a = (v-u)/t

Question 24

What is the no a formula?

Answer 24

s = 1/2 (u + v)t

Question 25

What is the no u formula?

Answer 25

s = vt - 1/2at square

Question 26

What does each of these letters s u v a t represent?

Answer 26

s --> displacement u --> initial velocity v --> final velocity a --> acceleration t --> time

Question 27

What is the definition of acceleration?

Answer 27

Acceleration is the rate of change of velocity with respect to time.

Question 28

What is the SI unit of acceleration and how is it expressed as?

Answer 28

The SI unit for acceleration is ms to the power of -1 for s and s to the powerof -1. it is expressed as a = triangle (change in) velocity/ triangle (change in) time

Question 29

The acceleration of an object during its motion may change. Hence, average acceleration is ______________________ and instantaneous acceleration is ______________________.

Answer 29

The acceleration of an object during its motion may change. Hence, average acceleration is the total change in velocity divided by the time taken and instantaneous acceleration is the rate of change of velocity at a particular instant.

Question 30

Free-falling objects experience uniform acceleration of ________ towards the Earth in the absence of ____________.

Answer 30

Free-falling objects experience uniform acceleration of 9.81 m s (to the power of -2 for s) towards the Earth in the absence of air resistance.

Question 31

What are the information that can be obtained from the displacement-time graph?

Answer 31

(a) gradient = velocity (b) straight line --> uniform velocity

Question 32

What are the information that can be obtained from the velocity-time graph?

Answer 32

(a) gradient = acceleration (b) area = CHANGE in displacement (c) straight line--> uniform acceleration

Question 33

What can be obtained from the acceleration-time graph?

Answer 33

area = change in velocity

Question 34

If you are required to sketch the velocity-time graph based on an acceleration-time graph , what should you do?

Answer 34

Firstly, draw the velocity-time graph and then check if it is make sense --> check forward don't check backwards (from acceleration to velocity as it will be difficult) take note of the gradient if the gradient of acceleration is constant and positive, it means that the velocity should be increasing constantly (diagonal line) if acceleration is zero, it means that velocity does not change (gradient of velocity is also zero) if acceleration decreases and then increases the line will go down and then go up --> then you have to calculate which point will be the point where the line will go up by calculating the area surrounded by the axis and line for acceleration time to figure out the area which would give you the change in velocity

Question 35

A stone is thrown vertically upwards and allowed to fall freely. Describe the acceleration-time graph of the stone. Give a reason for your answer.

Answer 35

a horizontal line below the x-axis gravitational acceleration near the earth’s surface has a constant direction and magnitude regardless of the motion of the body.—> your answer needs to have two parts: magnitude, direction (since acceleration is a vector)

Question 36

“The acceleration of an object has a negative value. Thus the object must be decelerating.” State and explain whether you agree with this statement.

Answer 36

The object is speeding up if it was moving in the negative direction [i.e. The velocity also has a negative value]. Take note to use the words: speed up or slow down instead of using accelerating or decelerating. AVOID USING ACCELERATING AND DECELERATING.