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anzhelika [568]
3 years ago
9

Spot welding is used to fuse two sheets of metal together at one small spot. Two copper electrodes pinch the sheets together at

a point and then run a huge electric current through that point. The two sheets melt and flow together to form a spot weld. Why does this technique work only with relatively poor conductors of electricity such as stainless steel and not with excellent conductors such as copper?
Physics
1 answer:
hjlf3 years ago
7 0

Answer:

The power deposited in a metal is proportional to its electric resistance, so high-resistance metals heat more.

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Two racing boats set out from the same dock and speed away at the same constant speed of 104 km/h for half an hour (0.500 h), th
Zinaida [17]

Answer:

The blue boat traveled 6.1 km farther west than the green boat

The green boat traveled 10.7 km farther south than the blue boat

Explanation:

The equation for linear uniform speed movement is

X(t) = X0 + v * t

Since we have two coordinates (X, Y) we use

X(t) = X0 + vx * t

Y(t) = Y0 + vy * t

The dock will be the origin of coordinates so X0 and Y0 will be zero. The X axis will be pointing west and the Y axis south.

The blue boat moves with a direction 24° south of west, so it will have speeds:

vxb = 104 * cos(24) = 95 km/h

vyb = 104 * sin(24) = 42.3 km/h

And the green boat:

vxg = 104 * cos(37.7) = 82.3 km/h

vyg = 104 * sin(37.7) = 63.6 km/h

After half hour the boats will have arrived at positions

Xb = 95 * 0.5 = 47.5 km

Yb = 42.3 * 0.5 = 21.1 km

And

Xg = 82.3 * 0.5 = 41.4 km

Yg = 63.6 * 0.5 = 31.8 km

The difference in positions of the boats

47.5 - 41.4 = 6.1 km

31.8 - 21.1 = 10.7 km

5 0
3 years ago
A 4kg rock isn’t rolling 10m/s. Find it’s kinetic energy.
scoundrel [369]

Kinetic energy = (1/2) (mass) (speed)²

The rock's kinetic energy is not 

                           (1/2) (4 kg) (10 m/s)²

                      =   (1/2) (4 kg) (100 m²/s²)

                      =         200 Joules .

It may be more, or it may be less.  The only thing
we can be sure of is that it is not 200 Joules.
3 0
3 years ago
An object is dropped from a height of 25 meters. At what velocity will it hit the ground?
Goryan [66]
You can use Vf^2-Vi^2 = 2ax

Vf^2 - 0 = 2(9.81)(25)

Or you can use energy

mgh = 1/2mv^2

2gh =v^2

Same thing
6 0
3 years ago
Two skaters collide and grab on to each other on frictionless ice. One of them, of mass 77.0 kg, is moving to the right at 4.00
Alex777 [14]

Answer:3.31m/s², to the right

Explanation:

According to the law of conservation of momentum of a body, change in momentum of bodies before collision is equal to the change in momentum after collision.

Momentum = mass × velocity

M1 and M2 be the masses of the first and second skaters respectively

Let u1 and u2 be the velocities of the first and second skaters respectively.

v be their common velocity after collision

M1 = 77kg M2 = 66kg u1 = 4m/s² u2 = 2.5m/s²

According to the law we have

M1u1 + M2u2 = (M1+M2)v

77(4) + 66(2.5) = (77+66)v

308 + 165 = 143v

V = 473/143

V = 3.31m/s²

Their velocity after collision will become 3.31m/s²

They will both move towards the right after collision because the mass of the body moving to the right is higher than the other mass and the mass is also moving at a higher velocity than the other.

5 0
3 years ago
An electric fan is turned off, and its angular velocity decreases uniformly from 500 rev/min to 200 rev/min in 4.00 s.
Veseljchak [2.6K]

Answer:

a) -1.25 rev/s² and 23.3 rev

b)  2.67s

Explanation:

a) ωФ_o_z = (500 rev/min)(1min/ 60s) => 8.333 rev/s

ωФ_Z= (200 rev/min)(1min/ 60s) => 3.333rev/s

time 't'= 4 s

angular acceleration 'αФ_Z'=?

constant angular acceleration equation is given by,

ωФ_Z= ωФ_o_z + αФ_Zt

αФ_Z= (ωФ_Z - ωФ_o_z )/t => (3.333-8.333)/4

αФ_Z= -1.25 rev/s²

θ-θФ_o = ωФ_o_z t + 1/2αФ_Zt²

      =(8.333)(4) + 1/2 (-1.25)(4)²

      =23.3 rev

b) ωФ_Z=0   (comes to rest)

ωФ_o_z = 3.333 rev/s

αФ_Z= -1.25 rev/s²

ωФ_Z= ωФ_o_z + αФ_Zt

t= (ωФ_Z - ωФ_o_z)/αФ_Z => (0- 3.333)/-1.25

t= 2.67s

3 0
3 years ago
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