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Tanzania [10]
3 years ago
13

An electric circuit can have no current when a switch is closed. True False

Physics
1 answer:
igomit [66]3 years ago
4 0

Answer: False

Explanation: When a switch is closed the circuit is closed and thus the flow of current is on while when the switch is open, the circuit is open, and therefore there will be no flow of current in the circuit.

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3. A football is kicked with a speed of 35 m/s at an angle of 40°.
jarptica [38.1K]

a) 22.5 m/s

The initial vertical velocity is given by:

u_y = u sin \theta

where

u = 35 m/s is the initial speed

\theta=40^{\circ} is the angle of projection of the ball

Substituting into the equation, we find

u_y = (35)(sin 40)=22.5 m/s

b) 26.8 m/s

The initial horizontal velocity is given by:

u_x = u cos \theta

where

u = 35 m/s is the initial speed

\theta=40^{\circ} is the angle of projection of the ball

Substituting into the equation, we find

u_x = (35)(cos 40)=26.8 m/s

c) 2.30 s

The time it takes for the ball to reach the maximum heigth can be found by considering the vertical motion only. This is a uniformly accelerated motion (free-fall), so we can use the suvat equation

v_y = u_y + at

where

v_y is the vertical velocity at time t

u_y = 22.5 m/s

a=g=-9.8 m/s^2 is the acceleration of gravity (negative because it is downward)

At the maximum height, the vertical velocity becomes zero, v_y =0; substituting, we find the time t at which this happens:

0=u_y + gt\\t=-\frac{u_y}{g}=-\frac{22.5}{-9.8}=2.30 s

d) 25.8 m

The maximum height can also be found by considering the vertical motion only. We can use the following suvat equation:

s=u_y t + \frac{1}{2}gt^2

where

s is the vertical displacement at time t

u_y = 22.5 m/s

g=-9.8 m/s^2

Substituting t = 2.30 s, we find the displacement at maximum height, so the maximum height:

s=(22.5)(2.30)+\frac{1}{2}(-9.8)(2.30)^2=25.8 m

e) 123.3 m

In order to find how far does the ball lands, we have to consider the horizontal motion.

First of all, the time it takes for the ball to go back to the ground is twice the time needed for reaching the maximum height:

t=2(2.30 s)=4.60 s

Then, we consider the horizontal motion. There is no acceleration along this direction, so the horizontal velocity is constant:

v_x = 26.8 m/s

Therefore, the horizontal distance travelled during the whole motion is

d=v_x t = (26.8)(4.60)=123.3 m

So, the ball lands 123.3 m far from the initial point.

4 0
3 years ago
Question 1 (1 point)
IrinaK [193]
  1.  momentum  
  2. Yes, if the elephant is standing still.
  3. Fullback  
  4. impulse acting on it.  
  5. 2.25 N∙s
  6. A cannon firing.
  7. Inelastic  
  8. it stays the same
  9. When the cue ball contacts the other balls, momentum is transferred causing them to gain momentum and speed.
  10. less than 3 m/s      
<h3><u><em>these are all correct i got an 100%</em></u><em><u> </u></em></h3>
8 0
2 years ago
A train moving at a constant speed on a surface inclined upward at 10.0° with the horizontal travels a distance of 400 meters in
Amiraneli [1.4K]
If the velocity of the train is v=s/t, where s is the distance and t is time, then v=400/5=80m/s. To get the vertical component of the velocity we need to multiply the velocity v with a sin(α): Vv=v*sin(α), where Vv is the vertical component of the velocity and α is the angle with the horizontal. So:

Vv=80*sin(10)=80*0.1736=13.888 m/s. 

So the vertical component of the velocity of the train is Vv=13.888 m/s.
7 0
3 years ago
If the force of gravity changes what will happen and what would cause it to change?
FromTheMoon [43]
We will fall to pluto.
5 0
3 years ago
Which of the following are ways the rising human population can lower their impact on the Earth's spheres and climate change? Se
Tju [1.3M]

a and c because its right im out of college

3 0
3 years ago
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