HARD
AS and A Level
IMPORTANT
Earn 100

A lion is watching a zebra from 35 m behind it. Both are stationary. The lion then starts chasing by accelerating at a constant rate of 3 m s-2 for 5 s. Once at top speed the lion maintains that speed for 3 s before decelerating at 0.5 m s-2. The zebra starts moving 1 s after the lion started, accelerating at a constant rate of 2 m s-2 for 7 s before maintaining a constant speed.

Show that the gap between them at time t s, for t>8, after the start of the lion's motion is given by 14t2-5t+512 and, hence, determine when the lion catches the zebra, or when the lion gets closest and how close it gets.

Important Questions on Velocity and Acceleration

HARD
AS and A Level
IMPORTANT

A car is behind a tractor on a single-lane straight road with one lane in each direction. Both are moving at 15 m s-1. The speed limit is 25 m s-1, so the car wants to overtake. The safe distance between the car and the tractor is 20 m.

To overtake, the car goes onto the other side of the road and accelerates at a constant rate of 2 m s-2 until reaching the speed limit, when it continues at constant speed. Show that the distance the car is ahead of the tractor at time t s after it starts to accelerate is given by t2-20 for 0<t5, and deduce that the car is not a safe distance ahead of the tractor before reaching the speed limit.

HARD
AS and A Level
IMPORTANT

A car is behind a tractor on a single-lane straight road with one lane in each direction. Both are moving at 15 m s-1. The speed limit is 25 m s-1, so the car wants to overtake. The safe distance between the car and the tractor is 20 m.

The car pulls in ahead of the tractor once it is a safe distance ahead. Find the total time taken from the start of the overtaking manoeuvre until the car has safely overtaken the tractor.

HARD
AS and A Level
IMPORTANT

A car is behind a tractor on a single-lane straight road with one lane in each direction. Both are moving at 15 m s-1. The speed limit is 25 m s-1, so the car wants to overtake. The safe distance between the car and the tractor is 20 m.

To overtake safely on the single-lane road, when the car returns to the correct side of the road in front of the tractor there must be a gap between the car and oncoming traffic of at least 20 m. Assuming a car travelling in the opposite direction is moving at the speed limit, find the minimum distance it must be from the initial position of the overtaking car at the point at which it starts to overtake.

HARD
AS and A Level
IMPORTANT
Two hockey players are practising their shots. They are 90 m apart and hit their balls on the ground directly towards each other. The first player hits his ball at 6 m s-1 and the other hits hers at 4 m s-1. Both balls decelerate at 0.1 m s-2. Find the distance from the first player when the balls collide.
HARD
AS and A Level
IMPORTANT

The sketch shows a velocity-time graph for a skier going down a slope. Given that the skier covers 80 m during the first stage of acceleration, find the total distance covered.

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HARD
AS and A Level
IMPORTANT
Two trains are travelling towards each other, one heading north at a constant speed of u m s-1 and the other heading south at a constant speed of v m s-1. When the trains are a distance d m apart, a fly leaves the northbound train at a constant speed of w m s-1. As soon as it reaches the other train, it instantly turns back travelling at w m s-1 in the other direction. Show that the fly meets the southbound train having travelled a distance of wdw+v and returns to the northbound train when the train has travelled a distance of 2uwd(w+v)(w+u).
HARD
AS and A Level
IMPORTANT

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The diagram shows the velocity-time graph for a particle P which travels on a straight line AB, where v m s-1 is the velocity of P at time t s. The graph consists of five straight line segments. The particle starts from rest when t=0 at a point X on the line between A and B and moves towards A. The particle comes to rest at A when t=2.5.

Given that the distance XA is 4 m, find the greatest speed reached by P during this stage of the motion.

HARD
AS and A Level
IMPORTANT

Question Image

The diagram shows the velocity-time graph for a particle P which travels on a straight line AB, where v m s-1 is the velocity of P at time t s. The graph consists of five straight line segments. The particle starts from rest when t=0 at a point X on the line between A and B and moves towards A. The particle comes to rest at A when t=2.5.

In the second stage, P starts from rest at A when t=2.5 and moves towards B. The distance AB is 48 m. The particle takes 12 s to travel from A to B and comes to rest at B. For the first 2 s of this stage P accelerates at 3 m s-2, reaching a velocity of V m s-1. Find

the value of V,