PHYSICS HIGH SCHOOL

What is happening if energy input remains constant and voltage remains the same in a circuit, but the current decreases?The resistance has increased.
The volts have decreased.
The power has increased.

Answers

Answer 1
Answer:

If energy input remains constant and voltage remains the same in a circuit, but the current decreases, the power has increased. It is presented in the equation P = VI where P is power, V is voltage and I is current.

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I have three questions. John has to hit a bottle with a ball to win a prize. He throws a 0.4 kg ball with a velocity of 18 m/s. It hits a 0.2 kg bottle, and the bottle flies forward at 25 m/s. How fast is the ball traveling after hitting the bottle? 2. Someone fires a 0.04 kg bullet at a block of wood that has a mass of 0.5 kg. (The block of woof is sitting on a frictionless surface, so it moves freely when the bullet hits it). The wood block is initially at rest. The bullet is traveling 300 m/s when it hits the wood block and sticks inside it. Now the bullet and the woof block move together as one object. How fast are they traveling?

3. A big league hitter attacks a fastball. The ball has a mass of 0.16 kg. It is pitched at 38 m/s. After the player hits the ball, it is now traveling 44 m/s in the opposite direction. The impact lasted 0.002 seconds. How big of a force did the ballplayer put on that ball?

Answers

1. 5.5 m/s

We can solve the problem by applying the law of conservation of momentum. The total momentum before the collision must be equal to the total momentum after the collision, so we have:

m_1 u_1 + m_2 u_2 = m_1 v_1 + m_2 v_2

where

m1 = 0.4 kg is the mass of the ball

u1 = 18 m/s is the initial velocity of the ball

m2 = 0.2 kg is the mass of the bottle

u2 = 0 is the initial velocity of the bottle (which is initially at rest)

v1 = ? is the final velocity of the ball

v2 = 25 m/s is the final velocity of the bottle

Substituting and re-arranging the equation, we can find the final velocity of the ball:

v_1 = (m_1 u_1 - m_2 v_2)/(m_1)=((0.4 kg)(18m/s)-(0.2 kg)(25 m/s))/(0.4 kg)=5.5 m/s


2. 22.2 m/s

We can solve the problem again by using the law of conservation of momentum; the only difference in this case is that the bullet and the block, after the collision, travel together at the same speed v. So we can write:

m_1 u_1 + m_2 u_2 = (m_1 +m_2) v

where

m1 = 0.04 kg is the mass of the bullet

u1 = 300 m/s is the initial velocity of the bullet

m2 = 0.5 kg is the mass of the block

u2 = 0 is the initial velocity of the block (which is initially at rest)

v = ? is the final velocity of the bullet+block, which stick and travel together

Substituting and re-arranging the equation, we can find the final velocity of bullet+block:

(m_1 u_1)/(m_1 +m_2)=((0.04 kg)(300 m/s))/(0.04 kg+0.5 kg)=22.2 m/s


3. 6560 N

The impulse exerted on the ball is equal to its change in momentum:

I=\Delta p (1)

The impulse can be rewritten as product between force and time of collision:

I=F \Delta t

while the change in momentum of the ball is equal to the product between its mass and the change in velocity:

\Delta p = m\Delta v = m(v_f -v_i)

So, eq.(1) becomes

F \Delta t = m(v_f -v_i)

where:

F = ? is the unknown force

\Delta t = 0.002 s is the duration of the impact

m = 0.16 kg is the mass of the ball

v_f = 44 m/s is the final velocity of the ball

v_i = -38 m/s is its initial velocity (we must add a negative sign, since it is in opposite direction to the final velocity)

So, by using the equation, we can find the force:

F=(m (v_f -v_i))/(\Delta t)=((0.16 kg)(44 m/s-(-38 m/s)))/(0.002 s)=6560 N

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Answers

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Big Al stands on a skateboard at a rest and throws a 0.5-kilogram rock at a velocity of 10.0 m /sec. Big Al moves back at 0.05 m/sec. What is the combined mass of Big Al and the skateboard?

Answers

let
his and skateboard's combined mass is x
we know
F1=-F2
0.5kg*10m/s=-0.05m/s xkg
5=0.05x(minus cancel with the m/s as it represented the opposite direction of velocity and now there is no velocity in this equation.. so minus is avoidable. and the kgs cancel out)
x=10
so their combined mass is a 100 kg.. (I hope I didn't mess thing up for you)

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Answers

The vacuum layer will prevent heat losses due to conduction and convection completely as it will provide no medium for these phenomena.

Answer:

insulator

Explanation:

The term “radiation” refers to hot materials inside the Earth rising towards Earth’s surface, cooling, and sinking back down.

Answers

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What is this equation for?

Answers

That's the equation for the efficiency of any machine or other system that you use to change energy from one form to another. It says that the efficiency of that device is equal to the work or energy that comes out of it divided by the work or energy that you put into it.
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