Podcast
Questions and Answers
How does displacement differ from distance?
How does displacement differ from distance?
- Displacement is the total length of travel, while distance is the change in position.
- Displacement is always greater than or equal to distance.
- Displacement considers the direction of motion, whereas distance is irrespective of direction. (correct)
- Displacement is a scalar quantity, while distance is a vector quantity.
A student walks 6 m East, 4 m South, 6 m West, and finally 4 m North. What is the student's total displacement?
A student walks 6 m East, 4 m South, 6 m West, and finally 4 m North. What is the student's total displacement?
- 4 m North
- 0 m (correct)
- 20 m
- 10 m
An object moves along a circle. The radius, r, of the circle is 3 m. What is the object's displacement after traveling halfway around the circle and what is the distance?
An object moves along a circle. The radius, r, of the circle is 3 m. What is the object's displacement after traveling halfway around the circle and what is the distance?
- Displacement = 0 m, Distance = $3\pi$ m
- Displacement = $3\pi$ m, Distance = 6 m
- Displacement = 6 m, Distance = $3\pi$ m (correct)
- Displacement = 6 m, Distance = 0 m
What distinguishes velocity from speed?
What distinguishes velocity from speed?
An object moves in a circle at a constant speed. Which statement is true?
An object moves in a circle at a constant speed. Which statement is true?
Which method is used to determine instantaneous velocity from a displacement-time graph?
Which method is used to determine instantaneous velocity from a displacement-time graph?
How is average speed calculated on a displacement-time graph?
How is average speed calculated on a displacement-time graph?
A car accelerates from rest to 20 m/s in 5 seconds. What is the car's acceleration?
A car accelerates from rest to 20 m/s in 5 seconds. What is the car's acceleration?
Which statement accurately describes acceleration?
Which statement accurately describes acceleration?
Which of the following is correct regarding this graph?
Which of the following is correct regarding this graph?
An object's acceleration increases from zero, reaches a maximum, and then decreases back to zero. Which graph best represents the object's velocity over time?
An object's acceleration increases from zero, reaches a maximum, and then decreases back to zero. Which graph best represents the object's velocity over time?
A car starts from rest and accelerates uniformly at 2 m/s² for 5 seconds. What is its final velocity?
A car starts from rest and accelerates uniformly at 2 m/s² for 5 seconds. What is its final velocity?
An object moves with an initial velocity of 5 m/s and accelerates uniformly at 3 m/s² for 4 seconds. What distance does it cover during this time?
An object moves with an initial velocity of 5 m/s and accelerates uniformly at 3 m/s² for 4 seconds. What distance does it cover during this time?
A car accelerates from 10 m/s to 30 m/s over a distance of 200 m. What is the car's acceleration?
A car accelerates from 10 m/s to 30 m/s over a distance of 200 m. What is the car's acceleration?
Which vehicle completes the 50.0 km trip in the shortest amount of time?
Which vehicle completes the 50.0 km trip in the shortest amount of time?
A stone is thrown horizontally from the top of a vertical cliff. What initial condition is true?
A stone is thrown horizontally from the top of a vertical cliff. What initial condition is true?
A stone is thrown horizontally from the top of a vertical cliff. What is vertical acceleration?
A stone is thrown horizontally from the top of a vertical cliff. What is vertical acceleration?
A stone is thrown horizontally from the top of a vertical cliff. What happens if air resistance is no longer negligible?
A stone is thrown horizontally from the top of a vertical cliff. What happens if air resistance is no longer negligible?
In projectile motion, what is the relationship between the launch angle and the range of the projectile, assuming all other factors are constant?
In projectile motion, what is the relationship between the launch angle and the range of the projectile, assuming all other factors are constant?
What is the primary cause of air resistance?
What is the primary cause of air resistance?
How does increasing the surface area of a falling object affect air resistance?
How does increasing the surface area of a falling object affect air resistance?
What causes a falling object to reach terminal velocity?
What causes a falling object to reach terminal velocity?
What is the net force acting on an object when it has reached terminal velocity?
What is the net force acting on an object when it has reached terminal velocity?
Terminal velocity is achieved when an object has a ...
Terminal velocity is achieved when an object has a ...
Which of the following is true when drag equals the force due to gravity on an object?
Which of the following is true when drag equals the force due to gravity on an object?
How does opening a parachute affect a parachutist's motion?
How does opening a parachute affect a parachutist's motion?
What does the second terminal velocity of a parachutist represent?
What does the second terminal velocity of a parachutist represent?
A ball is thrown upwards. At the peak of its motion, which of the following is true?
A ball is thrown upwards. At the peak of its motion, which of the following is true?
A car is traveling at 20 m/s when the driver applies the brakes, causing a uniform deceleration of 4 m/s². How far does the car travel before coming to a stop?
A car is traveling at 20 m/s when the driver applies the brakes, causing a uniform deceleration of 4 m/s². How far does the car travel before coming to a stop?
Two objects are dropped simultaneously from the same height. Object A has a larger surface area than Object B. Assuming air resistance is significant, which object will reach the ground first?
Two objects are dropped simultaneously from the same height. Object A has a larger surface area than Object B. Assuming air resistance is significant, which object will reach the ground first?
A projectile is launched with an initial velocity $v$ at an angle $\theta$ with respect to the horizontal. Which of the following statements is true about the horizontal component of the velocity, assuming air resistance is negligible?
A projectile is launched with an initial velocity $v$ at an angle $\theta$ with respect to the horizontal. Which of the following statements is true about the horizontal component of the velocity, assuming air resistance is negligible?
A biker travels at 25 kmh⁻¹ for the first 2 hours and then at 60 kmh⁻¹ for the next 3 hours, what is his average speed?
A biker travels at 25 kmh⁻¹ for the first 2 hours and then at 60 kmh⁻¹ for the next 3 hours, what is his average speed?
An object has a mass of 4 kg, a force of 20 N is applied on it, what distance is covered when this force is applied for 2 seconds?
An object has a mass of 4 kg, a force of 20 N is applied on it, what distance is covered when this force is applied for 2 seconds?
Which situation correctly shows a displacement of zero and a distance travelled ≠0?
Which situation correctly shows a displacement of zero and a distance travelled ≠0?
Which formula is correct for calculating the height? (Projectile achieve that height from point of projection; $t_2$ = second time when it achievements achieve same height)
Which formula is correct for calculating the height? (Projectile achieve that height from point of projection; $t_2$ = second time when it achievements achieve same height)
A ball is thrown upwards at time $t=0$. The graph shows the variation with time of the height of the ball. Assuming $T$ is the time the ball returns to the initial height, what formula would you use to determine the height h at time t?
A ball is thrown upwards at time $t=0$. The graph shows the variation with time of the height of the ball. Assuming $T$ is the time the ball returns to the initial height, what formula would you use to determine the height h at time t?
Flashcards
Describing motion
Describing motion
The motion of objects described using words.
Distance
Distance
The total length of travel irrespective of direction.
Displacement
Displacement
The distance moved in a particular direction; object's overall change in position.
Speed
Speed
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Velocity
Velocity
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Constant speed, changing velocity
Constant speed, changing velocity
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Instantaneous Speed/Velocity
Instantaneous Speed/Velocity
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Instantaneous velocity
Instantaneous velocity
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Average Speed/Velocity
Average Speed/Velocity
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Acceleration
Acceleration
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Projectile motion
Projectile motion
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Air resistance or drag
Air resistance or drag
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Terminal velocity
Terminal velocity
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Study Notes
A1: Kinematics
- Subtopic 2.1 covers describing motion with words including discussion of distance, displacement, speed, velocity, and acceleration
Distance and Displacement
- Motion of objects is described by words
- Distance refers to the total length of travel, regardless of direction
- Displacement refers to distance moved in a particular direction of an object
- Distance is a scalar quantity
- Displacement is a vector quantity
- The SI unit for both distance and displacement: metre (m)
- Common units for both: kilometre (km) and centimetre (cm)
Example: Student Walking
- A student walks 4 m East, 2 m South, 4 m West, and finally 2 m North
- The total distance travelled is 12m
- The total displacement is 0 m, as the student ends up where the started
- The 4 m east is "canceled by" the 4 m west, and the 2 m south is "canceled by" the 2 m north
Speed and Velocity
- Speed is the rate of change of distance
- Velocity is the distance travelled in a specific direction
- Velocity is also defined as the rate of change of displacement
- Speed is a scalar quantity
- Velocity is a vector quantity
Constant Speed vs Velocity
- An object moving in a circle at a constant speed has a changing velocity
- This is because its direction is continuously changing
Instantaneous Speed / Velocity
- Instantaneous speed or velocity refers to the speed or velocity of an object at a specific point in time
- This concept applies to objects moving at constant velocity or accelerating
- Acceleration is shown by a curved line on a displacement-time graph
- An accelerating object has a changing velocity
- To determine instantaneous velocity on a displacement-time graph:
- Draw a tangent at the required time
- Calculate the gradient of that tangent
Average Speed / Velocity
- Average speed or velocity is the total distance or displacement divided by the total time
- To find the average velocity on a displacement-time graph, divide the total displacement (y-axis) by the total time (x-axis)
- This method applies to curved or straight lines on displacement-time graphs
Acceleration
- Acceleration is the change in velocity over time
- Measured in m/s² or ms-2
- The formula for acceleration is
- a = Δv / Δt
- a = (v - u) / t
- V is the final velocity
- U is the initial velocity
Equations of Motion
- Equation 1: v = u + at
- Acceleration = Change in velocity / time
- Equation 2: s = (u + v)t / 2
- Average velocity = (u + v) / 2
- Average velocity = total distance / total time
- Equation 3: s = ut + 1/2 at²
- Equation 4: v2 = u² + 2as
- Where:
- t = time
- s = displacement
- u = initial velocity at t = 0
- v = final velocity after time t
- a = acceleration (10 m/s² if an object is falling)
What is a Projectile?
- Projectile motion occurs when an object is released and launched into the air at an angle relative to the ground
Horizontal Components of Projectile Motion
- At A (time = 0)
- Displacement = zero
- Velocity = v cos θ
- Acceleration = 0
- At B (time = t/2)
- Displacement = R/2
- Velocity = v cos θ
- Acceleration = 0
- At C (time = t)
- Displacement = R
- Velocity = v cos θ
- Acceleration = 0
Vertical Components of Projectile Motion
- At A
- Displacement = zero
- Velocity = v sin θ
- Acceleration = -g
- At B
- Displacement = h
- Velocity = zero
- Acceleration = -g
- At C
- Displacement = zero
- Velocity = -v sin θ
- Acceleration = -g
Suvat for Horizontal Motion
- Velocity = v = S/t = R = v cos Ot
- Because acceleration in horizontal motion is zero there is only one equation needed to define the motion
Suvat for Vertical Motion
- s = 1/2(u + v)t
- v² = u² + 2as
- s = ut + 1/2at²
- a = v-u/t
Calculating Maximum Range
- dx = (u² sin2θ) / g
- dx = range
- u = initial velocity
- θ = angle projectile is launched
- g = 9.81m/s²
- A projectile has the greatest range when launched at 45°
Projectile Motion Example
- A horizontally thrown stone from a 33 m cliff
- Initial horizontal velocity = 18 ms-1
- Air resistance is negligible
- Horizontal acceleration: ax = 0
- Vertical acceleration: ay = -10 ms-2
- Solving for time taken to reach sea level: t = 2.6 s
- Solving for distance from cliff base: Δx = 47 m
- Solving for the angle that the velocity makes with the surface of the sea: tan = 26/18 = tan-1(26/18) = 55º
Acceleration and Gravity
- Falling objects accelerate towards the ground at 10m/s² due to gravity
- The force of gravity always acts towards the centre of the Earth
- The atmosphere creates an upward force that slows down falling objects, Known as air resistance or drag
- The larger the surface area of the object, the larger the drag force
Relationship of Drag, Force, and Velocity
- Initially, the force of gravity is larger than the drag force, so the object accelerates
- As speed increases, so does drag, the acceleration decreases
- When drag equals the force due to gravity there is no resultant force and the acceleration is zero
- The object continues at terminal velocity
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