Calculus-Based Kinematics Examples

Velocity from a Position Function

The position of a particle moving along the x-axis is given by the equation x(t)=3t2−4t+2x(t) = 3t^2 - 4t + 2, where xx is in meters and tt is in seconds. Find the instantaneous velocity of the particle at t=2 st = 2 \text{ s}.

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Acceleration from a Velocity Function

A drone's velocity in the y-direction is given by vy(t)=4t3−2t m/sv_y(t) = 4t^3 - 2t \text{ m/s}. Determine its acceleration at t=1.5 st = 1.5 \text{ s}.

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Position from an Acceleration Function

An object starts from rest at the origin (x=0,t=0x=0, t=0). Its acceleration is given by a(t)=6t m/s2a(t) = 6t \text{ m/s}^2. Find its position at t=3 st = 3 \text{ s}.

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1D Constant Acceleration Examples

Constant-Acceleration Braking Distance

A car is traveling at 30 m/s30 \text{ m/s} when the driver sees a hazard and slams on the brakes. The car decelerates at a constant rate of 5 m/s25 \text{ m/s}^2. How far does the car travel before coming to a complete stop?

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Uniform Train Acceleration

A train accelerates uniformly from 15 m/s15 \text{ m/s} to 35 m/s35 \text{ m/s} over a distance of 500 m500 \text{ m}. Calculate the time it takes to cover this distance.

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Catch-Up Motion with an Accelerating Bus

A person is running at a constant speed of 6 m/s6 \text{ m/s} to catch a bus. When the person is 20 m20 \text{ m} behind the bus doors, the bus starts pulling away from the stop with a constant acceleration of 1 m/s21 \text{ m/s}^2. Does the person catch the bus? If so, how long does it take?

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Free Fall Examples

Free Fall from Rest

A rock is dropped from a 45 m45 \text{ m} high cliff. How long does it take to hit the ground? (Use g=9.8 m/s2g = 9.8 \text{ m/s}^2)

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Vertical Launch to Maximum Height

A ball is thrown straight up with an initial speed of 15 m/s15 \text{ m/s}. What is the maximum height it reaches?

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Downward Launch from Elevation

A coin is thrown vertically downwards from a balloon at an altitude of 300 m300 \text{ m} with an initial speed of 10 m/s10 \text{ m/s}. What is its velocity just before hitting the ground?

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Projectile Motion Examples

Horizontal Projectile from a 20 m Cliff

A rock is thrown horizontally off a 20 m20 \text{ m} high cliff at a speed of 15 m/s15 \text{ m/s}. How far from the base of the cliff does it land?

Horizontal Projectile from a 20 m Cliff Diagram

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Angled Projectile Range

A football is kicked at an angle of 40∘40^\circ to the horizontal with an initial speed of 25 m/s25 \text{ m/s}. Assuming level ground, calculate its horizontal range.

Angled Projectile Range Diagram

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Raised-Target Feasibility Check

A cannon fires a shell at 50 m/s50 \text{ m/s} and 30∘30^\circ above the horizontal. A target lies 40 m40 \text{ m} above the cannon's launch level. Determine whether the projectile can reach that elevation. If it can, find the horizontal distance to the target.

Raised-Target Feasibility Check Diagram

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Relative Velocity Examples

Relative Motion on a Moving Walkway

A passenger is walking at 1.5 m/s1.5 \text{ m/s} relative to a moving walkway in an airport. The walkway itself is moving at 2.0 m/s2.0 \text{ m/s} relative to the ground. What is the passenger's velocity relative to a stationary observer on the ground?

Relative Motion on a Moving Walkway Diagram

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Boat Crossing with River Current

A boat heading due North crosses a river with a velocity of 4 m/s4 \text{ m/s} relative to the water. The river flows due East at 3 m/s3 \text{ m/s}. What is the boat's resultant velocity relative to the riverbank?

Boat Crossing with River Current Diagram

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Relative Velocity of Two Vehicles

Car A is traveling East at 20 m/s20 \text{ m/s}. Car B is traveling North at 15 m/s15 \text{ m/s}. Find the velocity of Car A relative to Car B (v⃗AB\vec{v}_{AB}).

Relative Velocity of Two Vehicles Diagram

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Key Takeaways
  • Instantaneous velocity and acceleration require calculus (derivatives) if the acceleration is not constant.
  • In Projectile Motion, treat the horizontal and vertical motions as entirely independent problems linked only by time (tt).
  • Relative velocity requires defining a reference frame and using vector addition/subtraction.