The force required to slow the truck was -5020 N
Explanation:
First of all, we find the acceleration of the truck, which is given by

where
v is the final velocity
u is the initial velocity
t is the time
For the truck in this problem,
v = 11.5 m/s
u = 21.9 m/s
t = 2.88 s
So the acceleration is

where the negative sign means that this is a deceleration.
Now we can find the force exerted on the truck, which is given by Newton's second law:

where
m = 1390 kg is the mass of the truck
is the acceleration
And substituting,

So the closest answer among the option is -5020 N.
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Answer:
The wire now has less (the half resistance) than before.
Explanation:
The resistance in a wire is calculated as:

Were:
R is resistance
is the resistance coefficient
l is the length of the material
s is the area of the transversal wire, in the case of wire will be circular area (
).
So if the lenght and radius are doubled, the equation goes as follows:

So finally because the circular area is a square function, the resulting equation is half of the one before.
Answer:
a) 
b) 
Explanation:
Given:
- initial rotational speed of phonograph,

- final rotational speed of phonograph,

- time taken for the acceleration,

a)
Now angular acceleration:



b)
Using eq. of motion:



Answer:71 dB
Explanation:
Given
sound Level 
distance 
From sound Intensity





we know Intensity 




Sound level corresponding to 


