A box rests on the floor. If you pull sideways on the box with a 300 N force, but don't move it, what is the magnitude of the fr
1 answer:
The magnitude of the frictional force is B) 300 N
Explanation:
For this problem, we just have to consider the forces acting on the box in the horizontal direction.
There are only two forces in this direction:
- The pull applied by the man, of magnitude F=300 N, forward
- The frictional force, , acting backward
So the equation of motion for the box is
where
m is the mass of the box
a is its acceleration
However, the box is at rest, so its acceleration is zero:
a = 0
This means therefore that
And so the magnitude of the frictional force is equal to the pulling force:
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Answer:
B ) 1.5 m/s
Explanation:
For the apparent frequency reflected by enemy submarine , the Doppler effect formula is
F = F₀ ( V + v) / (V - v)
F anf F₀ are real and apparent frequency , V and v are velocity of sound and velocity of enemy submarine respectively.
ΔF / F₀ =
Put ΔF = 200; F₀ = 100000 and V = 1482
200 / 100000 =
v = 1.5 m s⁻¹ .
Answer:
His kinetic energy increases, potential energy decreases
The sum of kinetic and potential energy is a constant at any instant before he comes to rest.
Explanation:
Snowboarder is starting from a height and moving to the down direction. As he moves down his velocity increases, we know that kinetic energy is given by the expression , so as he moves his kinetic energy increases.
When the snowboarder is starting his potential energy is maximum(Potential energy = mgh), as he comes down his potential energy decreases.
Based on this we can conclude that the sum of potential energy and kinetic energy is a constant at any instant for a snowboarder before he comes to rest.
mgh+= Constant
Answer:
The speed of the soccer ball at height point is less than its initial speed
Explanation:
The initial velocity of the soccer can be written in vector form as
= v cos θ î + v sin θ j
where is initial velocity of the ball
v is the initial speed of the ball
Assume soccer ball is kicked at an angle θ with an horizontal and initial speed vm/s. Its horizontal component will be as,
= v cos θ
= v sin θ
At the maximum height, the vertical component becomes zero. therefore, the velocity of the soccer at the maximum point can be written as,
= v cos θ j
where, is velocity of the soccer ball at maximum height