Answer:
t = 4.28 s
Explanation:
The horizontal speed of a marble = 7 m/s
The horizontal displacement covered by the marble = 30 m
We need to find the time for which the marble is in air. Let the time is t. Using the formula for speed to find it as follows :

So, it will in the air for 4.28 s.
Complete question is;
Which action would increase the strength of the electric force between the balloon and the water?
A. Holding a magnet near the stream of water
B. Holding the balloon closer to the stream of water
C. Holding a magnet near the balloon
D. Moving the balloon farther away from the stream of water
Answer:
B. Holding the balloon closer to the stream of water
Explanation:
When we take a charged balloon near water, what happens is that it makes electrons to be pushed away which in turn leaves the area to be positively charged. This area is now attracted to the balloon and thus the strength of the electric force between the balloon and the water is increased.
Answer:
20.6 N
Explanation:
Friction equals normal force times coefficient of friction.
F = Fn μ
On level ground, normal force equal weight.
Fn = W
Therefore:
F = W μ
F = (685 N) (0.0300)
F = 20.6 N
The tangential velocity of the car is 124.5 m/s
Explanation:
The centripetal acceleration of an object in uniform circular motion is given by:

where
a is the acceleration
v is the tangential velocity
r is the radius of the circle
For the car in this problem, we have:
is the centripetal acceleration
r = 155 m is the radius of the turn
Solving for v, we find the tangential velocity of the car:

Learn more about centripetal acceleration:
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Answer:
A crane operator drops the cargo by turning off the electric current to the electromagnet. Electromagnets can be controlled by controlling the electric current. An electromagnet is stronger if there is more current flowing through it.
Explanation: