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Nesterboy [21]
3 years ago
6

You push very hard on a heavy desk, trying to move it. You do work on the desk:

Physics
1 answer:
frozen [14]3 years ago
3 0

Answer:

(C) Only if it starts moving

Explanation:

We know that work done is given by

W=F.d=Fdcos\Theta

So there are two case in which work done is zero

First case is that when force and displacement are perpendicular to each other

And other case is that when there is no displacement

So for work to be done there must have displacement, if there is no displacement then there is no work done

So option (c) will be the correct option

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A novelty golf ball of mass m is launched with an initial velocity v0 = (25i + 13j) m/s and then follows a parabolic trajectory.
SVEN [57.7K]

Explanation:

(a)

The initial vertical velocity is 13 m/s.  At the maximum height, the vertical velocity is 0 m/s.

v = at + v₀

0 = (-9.8) t + 13

t ≈ 1.33 s

(b)

Immediately prior to the explosion, the ball is at the maximum height.  Here, the vertical velocity is 0 m/s, and the horizontal velocity is constant at 25 m/s.

v = √(vx² + vy²)

v = √(25² + 0²)

v = 25 m/s

(c)

Momentum is conserved before and after the explosion.

In the x direction:

m vx = ma vax + mb vbx

m (25) = (⅓ m) (0) + (⅔ m) (vbx)

25m = (⅔ m) (vbx)

25 = ⅔ vbx

vbx = 37.5 m/s

And in the y direction:

m vy = ma vay + mb vby

m (0) = (⅓ m) (0) + (⅔ m) (vby)

0 = (⅔ m) (vby)

vby = 0 m/s

Since the vertical velocity hasn't changed, and since Fragment B lands at the same height it was launched from, it will have a vertical velocity equal in magnitude and opposite in direction as its initial velocity.

vy = -13 m/s

And the horizontal velocity will stay constant.

vx = 37.5 m/s

The velocity vector is (37.5 i - 13 j) m/s.  The magnitude is:

v = √(vx² + vy²)

v = √(37.5² + (-13)²)

v ≈ 39.7 m/s

7 0
4 years ago
Which of the following can easily be studied objectively? history meteorology sociology theology
Vilka [71]
<h2>Answer: meteorology </h2>

Explanation:

From the given options , meteorology is the only one that can be studied objectively, since it is an interdisciplinary science that relies on basic sciences such as physics and mathematics and applied sciences to the study of the atmosphere, the weather, the phenomena produced and the physical laws that govern it. In addition, meteorology uses objective techniques to study and predict the various phenomena that occur in the atmosphere.

Unlike history, sociology and theology, in which there is a possibility of the existence of some data are subjective and not true or only based on opinions <u>without scientific evidence</u>.

8 0
3 years ago
8. What is the S.l unit for mass?<br> A. kg<br> B. m/s2<br> D.N<br> C. m/s
katrin2010 [14]

Answer:

the answer is kg

Explanation:

because the s.i unit for mass is kilogram

3 0
3 years ago
What is the mass of a 1.2N book?
const2013 [10]

2.8 kg .............is the mass of a 1.2 N book.

7 0
3 years ago
Read 2 more answers
PUBLIC SCHOOLS
padilas [110]

Answer:

D. The cart is moving at a constant speed or velocity

Explanation:

Equilibrium is a state of body in which it is either at rest or moves with uniform velocity. The sum of forces acting on such a body is always zero and the sum of all the torques acting on it is also zero.

There are two types of equilibrium as follows:

Static Equilibrium: When a body is at rest it is said to be in static equilibrium.

Dynamic Equilibrium: When a body is moving with constant velocity, then it is said to be in dynamic equilibrium.

Hence, the correct option here will be:

<u>D. The cart is moving at a constant speed or velocity</u>

4 0
3 years ago
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