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A Level H2 Physics Practice Paper 4

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TuitionGoWhere Practice Paper - Physics H2 A-Level

TuitionGoWhere Practice Paper (AI)

Subject: Physics H2 (9478)
Level: A-Level
Paper: Practice Paper - Mechanics (Version 4 of 5)
Duration: 1 hour 30 minutes
Total Marks: 60

Name: ________________________
Class: ________________________
Date: ________________________

Instructions to Candidates

Answer all questions.
Write your answers in the spaces provided.
You may lose marks if you do not show your working or if you do not use appropriate units.
Take the acceleration of free fall $g = 9.81 \text{ m s}^{-2}$ .
At the end of the examination, fasten all your work securely together.

Section A: Structured Questions

Answer all questions in this section.

1. A car travels along a straight horizontal road. The velocity-time graph for the car is shown below.

(Imagine a graph: Velocity starts at 0, increases linearly to 20 m/s in 5s, stays constant at 20 m/s for 10s, then decreases linearly to 0 in 5s.)

(a) Calculate the acceleration of the car during the first 5 seconds.
[2]

(b) Calculate the total distance travelled by the car during the 20 seconds.
[2]

(c) Explain, with reference to Newton’s laws of motion, why the resultant force on the car is zero between $t = 5 \text{ s}$ and $t = 15 \text{ s}$ .
[2]

2. A block of mass $4.0 \text{ kg}$ rests on a rough horizontal surface. A horizontal force $F$ is applied to the block. The coefficient of static friction between the block and the surface is $0.50$ , and the coefficient of dynamic friction is $0.40$ .

(a) Calculate the minimum horizontal force $F$ required to just start the block moving.
[2]

(b) Once the block is moving, the force $F$ is maintained at the value calculated in (a). Calculate the acceleration of the block.
[3]

3. State the Principle of Conservation of Linear Momentum.
[2]

4. Two trolleys, A and B, move along a straight horizontal track. Trolley A has a mass of $2.0 \text{ kg}$ and moves with a velocity of $3.0 \text{ m s}^{-1}$ to the right. Trolley B has a mass of $1.0 \text{ kg}$ and is initially at rest. The trolleys collide and stick together.

(a) Calculate the common velocity of the trolleys after the collision.
[3]

(b) Determine whether this collision is elastic or inelastic. Show your working.
[3]

5. A satellite orbits the Earth in a circular orbit of radius $r$ .

(a) Derive the expression for the orbital speed $v$ of the satellite in terms of the gravitational constant $G$ , the mass of the Earth $M$ , and the radius $r$ .
[3]

(b) Explain why the satellite does not fall into the Earth despite being acted upon by the gravitational force.
[2]

Section B: Data-Based and Application Questions

Answer all questions in this section.

6. A student investigates the relationship between the extension $x$ of a spring and the load $F$ applied to it. The data obtained is plotted on a graph of $F$ against $x$ . The graph is a straight line passing through the origin with a gradient of $25 \text{ N m}^{-1}$ .

(a) Determine the spring constant $k$ of the spring.
[1]

(b) Calculate the elastic potential energy stored in the spring when the extension is $0.10 \text{ m}$ .
[2]

(c) The student repeats the experiment with a second identical spring connected in series with the first. Determine the effective spring constant of the combination.
[2]

7. A projectile is launched from ground level with an initial velocity of $20 \text{ m s}^{-1}$ at an angle of $30^\circ$ to the horizontal. Air resistance is negligible.

(a) Calculate the horizontal component of the initial velocity.
[1]

(b) Calculate the maximum height reached by the projectile.
[3]

8. A car of mass $1200 \text{ kg}$ travels up a slope inclined at $5.0^\circ$ to the horizontal at a constant speed of $15 \text{ m s}^{-1}$ . The resistive forces acting on the car total $400 \text{ N}$ .

(a) Calculate the component of the car's weight acting down the slope.
[2]

(b) Calculate the power developed by the car's engine.
[3]

9. A particle moves in a horizontal circle of radius $0.50 \text{ m}$ with a constant speed of $4.0 \text{ m s}^{-1}$ .

(a) Calculate the centripetal acceleration of the particle.
[2]

(b) State the direction of the centripetal acceleration.
[1]

(c) If the mass of the particle is $0.20 \text{ kg}$ , calculate the magnitude of the centripetal force acting on it.
[2]

10. The graph below shows the variation with time $t$ of the velocity $v$ of a ball bouncing vertically on a hard surface. Upward velocity is taken as positive.

(Imagine a graph: Velocity starts at +10 m/s, decreases linearly to -8 m/s at t=1.8s, then instantly jumps to +8 m/s, decreases to -6.4 m/s, etc.)

(a) Explain the significance of the gradient of the graph during the time the ball is in the air.
[1]

(b) Determine the height from which the ball was initially dropped.
[2]

(c) Calculate the loss in kinetic energy during the first impact with the ground if the mass of the ball is $0.050 \text{ kg}$ .
[3]

Section C: Long Structured Questions

Answer all questions in this section.

11. A uniform beam AB of length $4.0 \text{ m}$ and weight $200 \text{ N}$ is hinged at end A to a vertical wall. The beam is held horizontal by a cable attached to end B and to the wall at a point $3.0 \text{ m}$ above A. A load of $500 \text{ N}$ is suspended from the beam at a distance of $1.0 \text{ m}$ from A.

(a) Draw a free-body diagram showing all the forces acting on the beam.
[3]

(b) Calculate the tension in the cable.
[4]

12. A rocket of initial mass $1.5 \times 10^4 \text{ kg}$ is launched vertically from rest. The engines produce a constant thrust of $2.0 \times 10^5 \text{ N}$ . Assume the mass of the rocket remains constant for the first 10 seconds of flight and air resistance is negligible.

(a) Calculate the initial acceleration of the rocket.
[3]

(b) Calculate the velocity of the rocket after 10 seconds.
[2]

(c) In reality, the mass of the rocket decreases as fuel is burned. Explain qualitatively how this affects the acceleration of the rocket, assuming the thrust remains constant.
[2]

13. A simple pendulum consists of a bob of mass $0.50 \text{ kg}$ attached to a light inextensible string of length $1.2 \text{ m}$ . The bob is pulled aside until the string makes an angle of $10^\circ$ with the vertical and then released from rest.

(a) Show that the vertical height $h$ through which the bob falls is approximately $0.018 \text{ m}$ .
[2]

(b) Calculate the maximum speed of the bob as it passes through the lowest point of its swing.
[3]

14. Two stars, each of mass $M$ , orbit their common centre of mass in circular orbits of radius $R$ . The distance between the stars is $2R$ .

(a) Show that the gravitational force between the stars is given by $F = \frac{GM^2}{4R^2}$ .
[2]

(b) Derive an expression for the period $T$ of the orbit in terms of $G$ , $M$ , and $R$ .
[4]

15. A block of mass $2.0 \text{ kg}$ slides down a rough inclined plane from rest. The plane is inclined at $30^\circ$ to the horizontal. The coefficient of dynamic friction between the block and the plane is $0.20$ . The block travels a distance of $5.0 \text{ m}$ down the plane.

(a) Calculate the work done against friction.
[3]

(b) Use the principle of conservation of energy to calculate the speed of the block after it has travelled $5.0 \text{ m}$ .
[4]

16. A car travels around a banked track of radius $50 \text{ m}$ . The track is banked at an angle of $20^\circ$ to the horizontal. There is no friction between the tyres and the track.

(a) Draw a free-body diagram for the car, showing the weight and the normal reaction force.
[2]

(b) Derive an expression for the speed $v$ at which the car can travel without slipping up or down the bank, in terms of $g$ , $r$ , and $\theta$ .
[3]

17. An object is projected horizontally from the top of a cliff with a speed of $15 \text{ m s}^{-1}$ . It hits the ground $3.0 \text{ s}$ later.

(a) Calculate the height of the cliff.
[2]

(b) Calculate the horizontal distance from the base of the cliff to the point where the object hits the ground.
[2]

18. A spring of spring constant $k = 100 \text{ N m}^{-1}$ is compressed by $0.20 \text{ m}$ . A ball of mass $0.10 \text{ kg}$ is placed against the spring. The spring is released, launching the ball vertically upwards.

(a) Calculate the elastic potential energy stored in the spring before release.
[2]

(b) Assuming all the elastic potential energy is converted to gravitational potential energy, calculate the maximum height reached by the ball above its release point.
[3]

19. A uniform ladder of length $5.0 \text{ m}$ and weight $200 \text{ N}$ rests against a smooth vertical wall and on a rough horizontal ground. The foot of the ladder is $3.0 \text{ m}$ from the wall. A man of weight $800 \text{ N}$ stands on the ladder at a distance of $2.0 \text{ m}$ from the foot of the ladder (measured along the ladder).

(a) Calculate the normal reaction force exerted by the ground on the ladder.
[2]

(b) Calculate the frictional force exerted by the ground on the ladder.
[4]

20. A satellite of mass $m$ is in a geostationary orbit around the Earth.

(a) State two conditions required for a satellite to be in a geostationary orbit.
[2]

(b) Explain why a geostationary satellite must orbit directly above the equator.
[2]

(c) The radius of the geostationary orbit is $4.2 \times 10^7 \text{ m}$ . Calculate the linear speed of the satellite.
[2]

End of Paper

Answers

TuitionGoWhere Practice Paper - Physics H2 A-Level (Answer Key)

Version 4 of 5 - Mechanics

1. (a) Acceleration $a = \frac{\Delta v}{\Delta t} = \frac{20 - 0}{5} = 4.0 \text{ m s}^{-2}$ . [2] (b) Distance = Area under graph. Area = Area of triangle (0-5s) + Area of rectangle (5-15s) + Area of triangle (15-20s). Area = $\frac{1}{2}(5)(20) + (10)(20) + \frac{1}{2}(5)(20) = 50 + 200 + 50 = 300 \text{ m}$ . [2] (c) Between $t=5$ and $t=15$ , velocity is constant. Therefore, acceleration is zero. According to Newton’s First Law (or Second Law with $a=0$ ), if acceleration is zero, the resultant force is zero. [2]

2. (a) Normal reaction $N = mg = 4.0 \times 9.81 = 39.24 \text{ N}$ . Max static friction $F_{s,max} = \mu_s N = 0.50 \times 39.24 = 19.62 \text{ N}$ . Minimum force $F = 19.6 \text{ N}$ (2 s.f.). [2] (b) Dynamic friction $F_d = \mu_d N = 0.40 \times 39.24 = 15.696 \text{ N}$ . Resultant force $F_{res} = F_{applied} - F_d = 19.62 - 15.696 = 3.924 \text{ N}$ . Acceleration $a = \frac{F_{res}}{m} = \frac{3.924}{4.0} = 0.981 \text{ m s}^{-2}$ . [3]

3. In a closed system (1 mark), the total linear momentum before an interaction (collision/explosion) is equal to the total linear momentum after the interaction, provided no external resultant force acts on the system (1 mark). [2]

4. (a) Conservation of momentum: $m_A u_A + m_B u_B = (m_A + m_B) v$ . $(2.0)(3.0) + (1.0)(0) = (2.0 + 1.0) v$ . $6.0 = 3.0 v \implies v = 2.0 \text{ m s}^{-1}$ . [3] (b) Initial KE = $\frac{1}{2} m_A u_A^2 = \frac{1}{2}(2.0)(3.0)^2 = 9.0 \text{ J}$ . Final KE = $\frac{1}{2} (m_A + m_B) v^2 = \frac{1}{2}(3.0)(2.0)^2 = 6.0 \text{ J}$ . Since KE is not conserved ( $9.0 \neq 6.0$ ), the collision is inelastic. [3]

5. (a) Gravitational force provides centripetal force: $\frac{GMm}{r^2} = \frac{mv^2}{r}$ [1] $\frac{GM}{r} = v^2$ [1] $v = \sqrt{\frac{GM}{r}}$ [1] (b) The gravitational force acts perpendicular to the velocity of the satellite. This force changes the direction of the velocity but not its magnitude, causing the satellite to follow a curved path (orbit) rather than falling straight down. The "fall" is matched by the curvature of the Earth. [2]

6. (a) Gradient of $F$ vs $x$ is $k$ . So $k = 25 \text{ N m}^{-1}$ . [1] (b) $E_p = \frac{1}{2} k x^2 = \frac{1}{2}(25)(0.10)^2 = 0.125 \text{ J}$ . [2] (c) For springs in series, $\frac{1}{k_{eff}} = \frac{1}{k_1} + \frac{1}{k_2}$ . $\frac{1}{k_{eff}} = \frac{1}{25} + \frac{1}{25} = \frac{2}{25}$ . $k_{eff} = 12.5 \text{ N m}^{-1}$ . [2]

7. (a) $v_x = v \cos \theta = 20 \cos 30^\circ = 17.32 \approx 17.3 \text{ m s}^{-1}$ . [1] (b) Vertical component $v_y = v \sin \theta = 20 \sin 30^\circ = 10 \text{ m s}^{-1}$ . At max height, $v_y = 0$ . Using $v^2 = u^2 + 2as$ : $0 = 10^2 + 2(-9.81)h$ . $19.62 h = 100 \implies h = 5.099 \approx 5.10 \text{ m}$ . [3] (c) Time to reach max height: $v = u + at \implies 0 = 10 - 9.81 t \implies t = 1.019 \text{ s}$ . Total time of flight = $2 \times t = 2.038 \approx 2.04 \text{ s}$ . [2]

8. (a) Component of weight down slope = $mg \sin \theta = 1200 \times 9.81 \times \sin 5.0^\circ = 1025.5 \approx 1026 \text{ N}$ . [2] (b) Since speed is constant, driving force $F_D$ balances resistive forces and weight component. $F_D = mg \sin \theta + F_{resist} = 1025.5 + 400 = 1425.5 \text{ N}$ . Power $P = F_D v = 1425.5 \times 15 = 21382.5 \approx 21.4 \text{ kW}$ . [3]

9. (a) $a = \frac{v^2}{r} = \frac{4.0^2}{0.50} = \frac{16}{0.50} = 32 \text{ m s}^{-2}$ . [2] (b) Towards the centre of the circle. [1] (c) $F = ma = 0.20 \times 32 = 6.4 \text{ N}$ . [2]

10. (a) The gradient represents the acceleration due to gravity ( $g$ ). [1] (b) Initial velocity $u = 10 \text{ m s}^{-1}$ (upwards). At max height, $v=0$ . $v^2 = u^2 + 2as \implies 0 = 10^2 + 2(-9.81)h$ . $h = \frac{100}{19.62} = 5.097 \approx 5.1 \text{ m}$ . [2] (c) KE before impact: $\frac{1}{2} m u^2 = \frac{1}{2}(0.050)(10)^2 = 2.5 \text{ J}$ (using magnitude of velocity just before impact, which is approx 8 m/s from graph? Wait, graph says -8 m/s is velocity after bounce? No, graph usually shows velocity just before and just after. Let's assume velocity just before is -8 m/s? No, standard graph: drops from +10, hits ground. If it bounces to +8, it hit with -8? Let's assume symmetry of drop/rise for simplicity or read graph. Graph description: "decreases linearly to -8 m/s". So $v_{before} = -8$ ? No, if dropped from 10m/s up, it returns with -10m/s if no loss. The graph says it goes to -8. So $v_{impact} = -8$ ? Or does it hit with -10 and rebound to +8? Correction based on standard physics problems: Usually, the slope is constant $g$ . If it starts at +10, it takes $10/9.81 \approx 1s$ to reach peak, then 1s to return to start level with -10. If the graph shows it hitting at -8, it implies energy loss during flight (air res) or the graph scale is specific. Let's assume the velocity just before impact is $v_1$ and just after is $v_2$ . From graph description: "decreases linearly to -8 m/s at t=1.8s". This implies $v_{before} = -8$ ? That's physically inconsistent with starting at +10 without air res. Let's assume the question implies the velocity just before impact is determined by the drop height. Let's stick to the graph values provided in the prompt's imagination: "Velocity starts at +10... decreases to -8". This implies the impact velocity is 8 m/s downwards? Or is -8 the rebound? "Instantly jumps to +8". So rebound is +8. Impact was -8? If impact velocity is 8 m/s and rebound is 8 m/s, KE loss is 0. That's unlikely. Let's re-read carefully: "decreases linearly to -8 m/s... instantly jumps to +8 m/s". This implies an elastic collision? No, usually it jumps to a lower value. Let's assume the standard case: Drop from height corresponding to $u=10$ . $v_{impact}$ should be $\approx 10$ . If graph shows -8, maybe air resistance? Let's calculate KE loss based on the graph values: $KE_{before} = \frac{1}{2}(0.050)(8)^2 = 1.6 \text{ J}$ ? (If v=8). $KE_{after} = \frac{1}{2}(0.050)(8)^2 = 1.6 \text{ J}$ . Loss = 0. This seems wrong for a "bouncing ball" question. Alternative interpretation: The graph goes from +10 to -10 (impact), then jumps to +8 (rebound). Let's assume $v_{before} = 10 \text{ m s}^{-1}$ (magnitude) and $v_{after} = 8 \text{ m s}^{-1}$ . $KE_{before} = \frac{1}{2}(0.050)(10)^2 = 2.5 \text{ J}$ . $KE_{after} = \frac{1}{2}(0.050)(8)^2 = 1.6 \text{ J}$ . Loss = $2.5 - 1.6 = 0.9 \text{ J}$ . [3]

11. (a) Diagram: Weight of beam (200N) down at centre (2m from A). Load (500N) down at 1m from A. Tension $T$ at B (4m from A) acting towards wall point (3m above A). Hinge reaction at A (horizontal $H_A$ and vertical $V_A$ ). [3] (b) Take moments about A. Clockwise moments: $(200 \times 2.0) + (500 \times 1.0) = 400 + 500 = 900 \text{ Nm}$ . Anticlockwise moment: Vertical component of Tension $\times$ distance. Angle of cable: $\tan \theta = 3/4 \implies \sin \theta = 3/5 = 0.6$ . Vertical component $T_y = T \sin \theta = 0.6 T$ . Moment = $0.6 T \times 4.0 = 2.4 T$ . $2.4 T = 900 \implies T = 375 \text{ N}$ . [4] (c) Horizontal equilibrium: $H_A = T_x$ . $T_x = T \cos \theta = 375 \times (4/5) = 375 \times 0.8 = 300 \text{ N}$ . [2]

12. (a) Weight $W = mg = 1.5 \times 10^4 \times 9.81 = 147150 \text{ N}$ . Resultant Force $F_{res} = \text{Thrust} - W = 200000 - 147150 = 52850 \text{ N}$ . $a = \frac{F_{res}}{m} = \frac{52850}{15000} = 3.52 \text{ m s}^{-2}$ . [3] (b) $v = u + at = 0 + 3.523 \times 10 = 35.2 \text{ m s}^{-1}$ . [2] (c) As mass $m$ decreases, and Thrust is constant, the resultant force ( $T - mg$ ) increases (since $mg$ decreases). Since $a = F_{res}/m$ , both the numerator increasing and denominator decreasing cause the acceleration to increase. [2]

13. (a) $h = L - L \cos \theta = L(1 - \cos \theta)$ . $h = 1.2 (1 - \cos 10^\circ) = 1.2 (1 - 0.9848) = 1.2 (0.0152) = 0.0182 \text{ m}$ . [2] (b) Conservation of Energy: $mgh = \frac{1}{2} mv^2$ . $v = \sqrt{2gh} = \sqrt{2 \times 9.81 \times 0.0182} = \sqrt{0.357} = 0.597 \approx 0.60 \text{ m s}^{-1}$ . [3] (c) At lowest point, $T - mg = \frac{mv^2}{L}$ . $T = mg + \frac{mv^2}{L} = (0.50 \times 9.81) + \frac{0.50 \times (0.597)^2}{1.2}$ . $T = 4.905 + \frac{0.178}{1.2} = 4.905 + 0.148 = 5.05 \text{ N}$ . [3]

14. (a) Distance between centres is $2R$ . $F = \frac{G M_1 M_2}{d^2} = \frac{G M M}{(2R)^2} = \frac{GM^2}{4R^2}$ . [2] (b) Gravitational force provides centripetal force for one star orbiting the centre of mass (radius $R$ ). $\frac{GM^2}{4R^2} = \frac{M v^2}{R}$ . $\frac{GM}{4R} = v^2$ . $v = \sqrt{\frac{GM}{4R}}$ . Period $T = \frac{2\pi R}{v} = 2\pi R \sqrt{\frac{4R}{GM}} = 2\pi R \frac{2\sqrt{R}}{\sqrt{GM}} = 4\pi \sqrt{\frac{R^3}{GM}}$ . [4]

15. (a) Normal reaction $N = mg \cos 30^\circ = 2.0 \times 9.81 \times 0.866 = 16.99 \text{ N}$ . Friction $f = \mu N = 0.20 \times 16.99 = 3.398 \text{ N}$ . Work against friction $W_f = f \times d = 3.398 \times 5.0 = 16.99 \approx 17.0 \text{ J}$ . [3] (b) Loss in GPE = Gain in KE + Work against friction. $mgh = \frac{1}{2}mv^2 + W_f$ . $h = d \sin 30^\circ = 5.0 \times 0.5 = 2.5 \text{ m}$ . $2.0 \times 9.81 \times 2.5 = \frac{1}{2}(2.0)v^2 + 16.99$ . $49.05 = v^2 + 16.99$ . $v^2 = 32.06$ . $v = 5.66 \text{ m s}^{-1}$ . [4]

16. (a) Diagram: Weight $mg$ down. Normal reaction $N$ perpendicular to slope. No friction. [2] (b) Resolve $N$ : Vertical $N \cos \theta = mg$ . Horizontal $N \sin \theta = \frac{mv^2}{r}$ . Divide equations: $\tan \theta = \frac{v^2}{rg}$ . $v = \sqrt{rg \tan \theta}$ . [3] (c) $v = \sqrt{50 \times 9.81 \times \tan 20^\circ} = \sqrt{490.5 \times 0.364} = \sqrt{178.5} = 13.36 \approx 13.4 \text{ m s}^{-1}$ . [2]

17. (a) Vertical motion: $u_y = 0$ , $a = 9.81$ , $t = 3.0$ . $h = ut + \frac{1}{2}at^2 = 0 + \frac{1}{2}(9.81)(3.0)^2 = 44.145 \approx 44.1 \text{ m}$ . [2] (b) Horizontal motion: $v_x = 15$ , $t = 3.0$ . $d = v_x t = 15 \times 3.0 = 45 \text{ m}$ . [2] (c) $v_y = u_y + at = 0 + 9.81 \times 3.0 = 29.43 \text{ m s}^{-1}$ . $v_x = 15 \text{ m s}^{-1}$ . $v = \sqrt{v_x^2 + v_y^2} = \sqrt{15^2 + 29.43^2} = \sqrt{225 + 866.1} = \sqrt{1091.1} = 33.0 \text{ m s}^{-1}$ . [3]

18. (a) $E_p = \frac{1}{2} k x^2 = \frac{1}{2}(100)(0.20)^2 = 2.0 \text{ J}$ . [2] (b) $E_p = mgh \implies 2.0 = 0.10 \times 9.81 \times h$ . $h = \frac{2.0}{0.981} = 2.038 \approx 2.04 \text{ m}$ . [3] (c) 1. Air resistance acts on the ball. 2. Some energy is retained as kinetic energy in the spring/mass of the spring itself (or sound/heat during release). [2]

19. (a) Vertical equilibrium: $R_{ground} = W_{ladder} + W_{man} = 200 + 800 = 1000 \text{ N}$ . [2] (b) Take moments about the foot of the ladder (point A). Let length $L=5$ . Foot is 3m from wall, so height $H = \sqrt{5^2 - 3^2} = 4 \text{ m}$ . $\cos \theta = 3/5 = 0.6$ . $\sin \theta = 4/5 = 0.8$ . Moment of Wall Reaction $R_w$ (horizontal at top): $R_w \times 4$ (vertical distance). Moment of Ladder Weight: $200 \times (2.5 \cos \theta) = 200 \times 2.5 \times 0.6 = 300 \text{ Nm}$ . Moment of Man: Man is 2m along ladder. Horizontal dist from foot = $2 \cos \theta = 2 \times 0.6 = 1.2 \text{ m}$ . Moment = $800 \times 1.2 = 960 \text{ Nm}$ . Equilibrium: $4 R_w = 300 + 960 = 1260$ . $R_w = 315 \text{ N}$ . Horizontal equilibrium: Friction $F = R_w = 315 \text{ N}$ . [4]

20. (a) 1. Period of orbit is 24 hours (same as Earth's rotation). 2. Orbits in the same direction as Earth's rotation (West to East). [2] (b) To remain stationary relative to a point on Earth, the centripetal force must be directed towards the Earth's centre of rotation. This axis is the Earth's polar axis. Only an orbit above the equator has its centre at the Earth's centre and lies in the plane perpendicular to the axis of rotation, allowing the satellite to stay above the same latitude (0 degrees). [2] (c) $v = \frac{2\pi r}{T}$ . $T = 24 \times 3600 = 86400 \text{ s}$ . $v = \frac{2\pi (4.2 \times 10^7)}{86400} = \frac{2.639 \times 10^8}{86400} = 3054 \approx 3.05 \times 10^3 \text{ m s}^{-1}$ . [2]