3. A block with a force of the Earth of -300. N is moved at constant velocity over a horizontal surface by a force of +50.0 N ap
1 answer:
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Answer:
-4.0 N
Explanation:
Since the force of friction is the only force acting on the box, according to Newton's second law its magnitude must be equal to the product between mass (m) and acceleration (a):
(1)
We can find the mass of the box from its weight: in fact, since the weight is W = 50.0 N, its mass will be
And we can fidn the acceleration by using the formula:
where
v = 0 is the final velocity
u = 1.75 m/s is the initial velocity
t = 2.25 s is the time the box needs to stop
Substituting, we find
(the acceleration is negative since it is opposite to the motion, so it is a deceleration)
Therefore, substituting into eq.(1) we find the force of friction:
Where the negative sign means the direction of the force is opposite to the motion of the box.
The momentum of the car is 60,000 kg m/s
Explanation:
The momentum of an object is a vector quantity, whose magnitude is given by
where
m is the mass of the object
v is its velocity
For the car in this problem, we have
m = 2,000 kg
v = 30 m/s
Therefore, the magnitude of its momentum is
Learn more about momentum here:
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