Answer:
the  magnitude of the force that the wire will experience = 1.8 N
Explanation:
The force on a current carrying wire placed in a magnetic field is :
F = Idl × B
where:
I = current flowing through the wire
dl = length of the wire 
B = magnetic field
We can equally say that :

where : sin θ is the angle at which the orientation from the magnetic field  to the wire occurs = 30°
Then;

Given that:
L = 20 cm = 0.2 m
I = 6 A
B = 3 T
θ = 30°
Then:
F = 3 × 6 × 0.2 sin 30°
F = 1.8 N
Therefore, the  magnitude of the force that the wire will experience = 1.8 N
 
        
             
        
        
        
Answer:
B. 25 feet
Explanation:
In most cities in US, passenger car brakes must stop a car moving at 20 miles per hour at 25 feet. 
Therefore, the correct option is "B" 25 feet
 
        
                    
             
        
        
        
Answer:
Gravity and 
Air resistance
Explanation:
The two forces acting on a skydiver are gravitational force and air resistance. 
Gravitational force is a force that tends to pull all massive bodies towards the center of the earth. It works on all bodies that has mass. The larger or bigger the mass, the more the pull of gravity on the body. 
Air resistance is the drag of air on a body as it passes to it. It is resisting force. 
- When a sky diver jumps out of a plane, he/she encounters both gravity and air resistance. 
- It soon balances both force and attain terminal velocity. 
- Air resistance is a frictional force that opposes motion. 
- This frictional force pushes in the opposite direction of motion
- Motion direction is downward due to the celerity caused by gravity. 
 
        
                    
             
        
        
        
Answer:
0.8 seconds
Explanation:
F=ma
Let x be the seconds the force is applied.
m = 20kg
F = 50 Newtons (kg*m/sec^2)
acceleration, a, is provided for x seconds to increase the speed from 1 m/s to  3 m/s, an increase of 2m/s
Let's calculate the acceleration of the cart:
F=ma
(50 kg*m/s^2) = (20kg)*a
a = 2.5 m/s^2
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The acceleration is 2.5 m/s^2.  The cart increases speed by 2.5 m/s every second.  
We want the number of seconds it takes to add 2.0 m/sec to the speed:
(2.5 m/s^2)*x = 2.0 m/s
x = (2.0/2.5) sec
x = 0.8 seconds
 
        
             
        
        
        
Heat transferred - Work done = Internal Energy
Explanation:
- If there is more heat transfer than the work done, the energy difference is called internal energy 
- The first law of thermodynamics equation is given as ΔU=Q−W where, ΔU = Internal energy; Q = Heat transfer; W = Work done
- Heat = transfer of thermal energy between two bodies at different temperatures
- Work = force used to transfer energy between a system and its surroundings
- The First Law of Thermodynamics states - energy can be converted from one form to another with the interaction of heat, work and internal energy
- Energy cannot be created nor destroyed