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Vika [28.1K]
3 years ago
6

A man is throwing a spear from the top of a cliff, 5 metres from ground, at a 20° angle towards a fish that is 35 metres away. a

t what Velocity must the person throw to hit the fish and how long will it take?​

Physics
1 answer:
svlad2 [7]3 years ago
6 0

Answer:

Horizontal component of the initial velocity=v ×cos20°

horizontal displacement= 35m

time taken. (t)=35÷(v×cos20°)

vertical component of the initial velocity= v×sin20°

vertical displacement= -5m(since it is opposite to the direction of the initial velocity. )

application of s=ut+1/2at×t. vertically,

-5=vsin20°×t -1/2 gt×t

-5= vsin20×35/vcos20-1/2×10×35×35/(vcos20×vcos20)

simplify further to obtain v and hence find the time taken

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3 years ago
The magnetic field perpendicular to a single 16.7-cm-diameter circular loop of copper wire decreases uniformly from 0.750 T to z
sammy [17]

Answer:

1.24 C

Explanation:

We know that the magnitude of the induced emf, ε = -ΔΦ/Δt where Φ = magnetic flux and t = time. Now ΔΦ = Δ(AB) = AΔB where A = area of coil and change in magnetic flux = Now ΔB = 0 - 0.750 T = -0.750 T, since the magnetic field changes from 0.750 T to 0 T.

The are , A of the circular loop is πD²/4 where D = diameter of circular loop = 16.7 cm = 16.7 × 10⁻²m

So, ε = -ΔΦ/Δt = -AΔB/Δt= -πD²/4 × -0.750 T/Δt = 0.750πD²/4Δt.

Also, the induced emf ε = iR where i = current in the coil and R = resistance of wire = ρl/A where ρ = resistivity of copper wire =1.68 × 10⁻⁸ Ωm, l = length of wire = πD and A = cross-sectional area of wire = πd²/4 where d = diameter of wire = 2.25 mm = 2.25 × 10⁻³ m.

So, ε = iR = iρl/A = iρπD/πd²/4 = 4iρD/d²

So,  4iρD/d² = 0.750πD²/4Δt.

iΔt = 0.750πD²/4 ÷ 4iρD/d²

iΔt = 0.750πD²d²/16ρ.

So the charge Q = iΔt

= 0.750π(Dd)²/16ρ

= 0.750π(16.7 × 10⁻²m 2.25 × 10⁻³ m)²/16(1.68 × 10⁻⁸ Ωm)

= 123.76 × 10⁻² C

= 1.2376 C

≅ 1.24 C

4 0
4 years ago
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