Answer:
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Mechanical advantage of a machine is the ratio of the output force over the input force or M=Fo/Fi. Since M=1, Fi=Fo, or the input force is equal to the output force. This means that to raise the refrigerator that weighs 900 N, we need the same input force of 900 N, or Fo=Fi=900 N.
Coulomb's law:
Force = (<span>8.99×10⁹ N m² / C²<span>) · (charge₁) · (charge₂) / distance²
= (</span></span><span>8.99×10⁹ N m² / C²<span>) (1 x 10⁻⁶ C) (1 x 10⁻⁶ C) / (1.0 m)²
= (8.99×10⁹ x 1×10⁻¹² / 1.0) N
= 8.99×10⁻³ N
= 0.00899 N repelling.
Notice that there's a lot of information in the question that you don't need.
It's only there to distract you, confuse you, and see whether you know
what to ignore.
-- '4.0 kg masses'; don't need it.
Mass has no effect on the electric force between them.
-- 'frictionless table'; don't need it.
Friction has no effect on the force between them,
only on how they move in response to the force.
</span></span>
Answer:
F=5833.3 N N
Explanation:
Newton's second law applied to the car
F= m*a Formula (1)
F: Force in Newtons (N)
m : mass in kg
a: acceleration ( m/s²)
kinematics car
vf= v₀ + a*t Formula (2)
vf : final velocity (m/s)
v₀ : final velocity (m/s)
a : acceleration ( m/s²)
t : time t
Equivalences
1 km= 1000m
1 h = 3600 s
Data
m= 1000kg
v₀ = 90 km/h = 90*1000/3600 m/s = 25 m/s
vf= 0
t= 6 s
Problem Development
We calculate the acceleration replacing the data in the formula (2) :
0 = 25 + a*6
a= -25/6 = -4.16 m/s² ( The negative sign indicates that the car is braking)
We calculate the force is required to stop the car replacing the data in the formula (1)
-F = 1400 kg*(-4.16 m/s²)
F=5833.3 N
