A Porter carries a 25 kg suitcase a distance of 1 km. Explain why the Porter does no work
1 answer:
The Porter does no work because the force applied is perpendicular to the displacement
Explanation:
The work done by a force applied to an object is given by:
where
F is the magnitude of the force
d is the displacement
is the angle between the direction of the force and the displacement of the object
From the formula, we notice that:
- The work done is maximum when the force is parallel to the displacement (because )
- The work done is zero when the force is perpendicular to the displacement (because )
In this problem, Porter is carrying the suitcase: this means that the force he is applying is upward (to balance the weight of the suitcase, pulling down), while the displacement is in the horizontal direction: therefore, force and displacement are perpendicular, so the work done is zero.
Learn more about work:
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a) The kinetic energy (KE) of an object is expressed as the product of half of the mass (m) of the object and the square of its velocity (v²):
It is given:
v = 8.5 m/s
m = 91 kg
So:
b) We can calculate height by using the formula for potential energy (PE):
PE = m*g*h
In this case, h is eight, and PE is the same as KE:
PE = KE = 3,287.4 J
m = 91 kg
g = 9.81 m/s² - gravitational acceleration
h = ? - height
Now, let's replace those:
3,287.4= 91 * 9.81 * h
⇒ h = 3,287.4/(91*9.81) = 3,287.4/892.7 = 3.7 m
Answer:
The ball would have landed 3.31m farther if the downward angle were 6.0° instead.
Explanation:
In order to solve this problem we must first start by doing a drawing that will represent the situation. (See picture attached).
We can see in the picture that the least the angle the farther the ball will go. So we need to find the A and B position to determine how farther the second shot would go. Let's start with point A.
So, first we need to determine the components of the velocity of the ball, like this:
we pick the positive one, so it takes 0.317s for the ball to hit on point A.
so now we can find the distance from the net to point A with this time. We can find it like this:
Once we found the distance between the net and point A, we can similarly find the distance between the net and point B:
t= -0.9159s or t=0.468s
we pick the positive one, so it takes 0.468s for the ball to hit on point B.
so now we can find the distance from the net to point B with this time. We can find it like this:
So once we got the two distances we can now find the difference between them:
so the ball would have landed 3.31m farther if the downward angle were 6.0° instead.
