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A transformer has an input voltage of 4V, an output voltage of 8V and 50 turns on its primary coil. Assuming 100% efficiency, find the number of turns on the secondary coil.

Using Vp/Vs=Np/Ns, we can rearrange to get Ns= (VsNp)/VpSo, Ns = 8*50/4=100 turns.
JW
Answered by Joe W. • Physics tutor
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A projectile is launched from ground level with a speed of 25 m/s at an angle of 42° to the horizontal. What is the horizontal distance from the starting point of the projectile when it hits the ground?

Resolve the vertical velocity of the projectile (25sin42) and use v=u+at where v=-25sin42m/s, u=25sin42m/s, a=-9.8m/s/s to find t. t= (50sin42)/9.8= 3.41sResolve horizontal velocity (25cos42) and multiply by...
JW
Answered by Joe W. • Physics tutor
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Translate the following text into English

Mes copains vont souvent au jardin public près de l'école parce qu’on peut jouer au foot. C'est inquiétant le nombre de sans-abris qu'on y voit. Nous aimerions pouvoir donner de notre temps pour les aider. P...
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Answered by Joe W. • French tutor
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Write 5cos(theta) – 2sin(theta) in the form Rcos(theta + alpha), where R and alpha are constants, R > 0 and 0 <=alpha < 2 π Give the exact value of R and give the value of alpha in radians to 3 decimal places.

Use the formula cos(A+B)=cosAcosB-sinAsinB, Rcos(theta+alpha)=Rcos(alpha)cos(theta)-Rsin(alpha)sin(theta)5=Rcos(alpha)2=Rsin(alpha)tan(alpha)=2/5alpha= 0.381R=sqrt(5^2+2^2)=sqrt(29)So, 5cos(theta) – 2sin(the...
JW
Answered by Joe W. • Maths tutor
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The equation of the line L1 is y = 3x – 2 The equation of the line L2 is 3y – 9x + 5 = 0 Show that these two lines are parallel.

L1 is in the form y=mx+c where m is the gradient, 3.L2 can be rewritten as 3y=9x-5, then y=3x-(5/3) to reach y=mx+c. So, the gradient of L2 is 3.Therefore, both lines are parallel.
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Answered by Joe W. • Maths tutor
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