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BigorU [14]
3 years ago
15

A student pushes a box across a rough horizontal floor. If the amount of work done by the student on the box is 100 J and the am

ount of energy dissipated by friction is 40 J, what is the change in kinetic energy of the box
Physics
1 answer:
Archy [21]3 years ago
4 0

Answer:

60J

Explanation:

friction is the opposition to the motion of an object. Before a body can be set in motion, part of the energy or work-done must be used to overcome friction.

While kinetic energy is the energy associated with a body due to its motion.

Since friction tends to oppose the motion of a body,when a body start to move, some of the energy applied to the body to cause its motion is converted to heat due to friction.

Hence if a work-done of 100J is applied to a body that requires 40J of the work to overcome friction, the total change in the kinetic energy can be expressed as

K.E=100J-40J\\K.E=60J\\

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A textbook of mass 2.09 kg rests on a frictionless, horizontal surface. A cord attached to the book passes over a pulley whose d
Nutka1998 [239]

Answer:

The tension in the part of the cord attached to the textbook is 6.58 N.

Explanation:

Given that,

Mass of textbook = 2.09 kg

Diameter = 0.190 m

Mass of hanging book = 3.08 kg

Distance = 1.26 m

Time interval = 0.800 s

Suppose,we need to calculate the tension in the part of the cord attached to the textbook

We need to calculate the acceleration

Using equation of motion

y=ut+\dfrac{1}{2}at^2

a=\dfrac{2y}{t^2}

Put the value into the formula

a=\dfrac{2\times1.26}{0.800}

a=3.15\ m/s^2

We need to calculate the tension

When the book is moving with acceleration

Using formula of tension

T=ma

T=2.09\times3.15

T=6.58\ N

Hence, The tension in the part of the cord attached to the textbook is 6.58 N.

7 0
3 years ago
If you go to space at 15000 mph. how long would it take you at the same speed to reach mars
madreJ [45]

Answer:

if your going 15000 mph all you can do is accelerate  or go fast  unless there is a opposite

Explanation:

6 0
3 years ago
A meter stick is place in a very high-speed spaceship. What length would the astronauts say the meter stick was? What would the
Marysya12 [62]

Answer:

a) The astronauts would see the real length of the meter stick, i.e.  L₀

b) The length of the meter stick as measured by the stationary observer will be L = L_{0} }{\sqrt{(1-(\frac{v}{c} )^{2}  } }

Explanation:

a) Let the proper length of the meter stick be L₀

The meter stick and the astronauts on the on the space ship are on the same moving frame, therefore, they will see the exact length of the meter stick, that is, L₀

b) A stationary observer watching the space ship and meter stick travel past them will see a contracted length of the meter stick

The original length = L₀

Let the speed of the space ship = v

The contracted length, L, is related to the original length in the frame of rest by

L = L₀/γ......................(1)

Where γ = \frac{1}{\sqrt{(1-(\frac{v}{c} )^{2}  } } ....................(2)

Substituting equation (2) into (1)

L = L_{0} }{\sqrt{(1-(\frac{v}{c} )^{2}  } }

4 0
3 years ago
In the image of the underwater submarine (i can't upload it), if the only 2 forces acting on the submarine are the downward forc
shutvik [7]

K so I'm not completely sure about this...

but I believe the answer would be C. It will float upward

because the buoyancy, in the image, is stronger than the Gravitational pull.

Let me know if that is right or wrong plz

Hope it's right and helps tho!


4 0
3 years ago
Jumping up before the elevator hits. After the cable snaps and the safety system fails, an elevator cab free-falls from a height
noname [10]

Answer:

a)   I = 2279.5 N s , b) F = 3.80 10⁵ N, c)   I = 3125.5 N s  and d)  F = 5.21 10⁵ N

Explanation:

The impulse is equal to the variation in the amount of movement.

    I =∫ F dt = Δp

     I = mv_{f} - m v₀

Let's calculate the final speed using kinematics, as the cable breaks the initial speed is zero

   v_{f}² = V₀² - 2g y

   v_{f}² = 0 - 2 9.8 30.0

   v_{f} = √588

   v_{f} = 24.25 m/s

a) We calculate the impulse

   I = 94 24.25 - 0

   I = 2279.5 N s

b) Let's join the other expression of the impulse to calculate the average force

   I = F t

  F = I / t

  F = 2279.5 / 6 10⁻³

  F = 3.80 10⁵ N

just before the crash the passenger jumps up with v = 8 m / s, let's take the moments of interest just when the elevator arrives with a speed of 24.25m/s down and as an end point the jump up to vf = 8 m / n

c)     I = m v_{f} - m v₀

       I = 94 8 - 94 (-24.25)

       I = 3125.5 N s

d)     F = I / t

       F = 3125.5 / 6 10⁻³

       F = 5.21 10⁵ N

7 0
3 years ago
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