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A man who works for a moving company is loading a box onto a moving van. He pushes a 200N box up a 5m long ramp. If he pushes wi

OlgaM077 [116]

Answer:

η = 0.667 = 66.7%

Explanation:

The efficiency of the man can be given by the following formula:

η = output/input

where,

η = efficiency of man = ?

output = potential energy gain of the box = Wh

input = work done by man = Fd

Therefore,

$\eta = \frac{Wh}{Fd}$

where,

W = weight of box = 200 N

h = height gained by box = 1 m

F = force exerted by man = 60 N

d = length of ramp = 5 m

Therefore,

$\eta = \frac{(200\ N)(1\ m)}{(60\ N)(5\ m)}$

8 0

3 years ago

A football has a mass of 2 kg and it accelerates at 20 m/s2. What is its force? (You can use a calculator)

miskamm [114]

Answer:

Kent is making a scale model of his favorite train. The actual train is 12 feet long and 4 feet wide. Kent wants his mdth of his model if he uses the same ratio?

Explanation:

Kent is making a scale model of his favorite train. The actual train is 12 feet long and 4 feet wide. Kent wants his model to be 6 inches in length. Which would be the width of his modelhe uses the same ratio?

7 0

2 years ago

Read 2 more answers

One end of a horizontal spring with force constant 130.0 N/m is attached to a vertical wall. A 3.00 kg block sitting on the floo

Nuetrik [128]

Answer:

a) v = 0

b) The aceleration is 1.41 $m/s^{2}$

c) The block is accelerating away from the wall.

Explanation:

First, you need to think about the effect this constant force is causing in the spring: it causes a displacement in the equilibrium point of the system, therefore we need to know where it sits now:

At equilibrium no movement is present reducing friction to 0:

$\sum{F} = 0 = F_{spring} - F_{external}$

$F_{spring} = F_{external}$

$Kx = F_{external}$

$x = \frac{F_{external}}{K}=\frac{88}{130}=0.68m=68cm$

This means that the spring can be compressed with the single force up to 68 cm, Any further compression will cause an unbalanced system and the occilation of the mass.

The spring can't be compressed by the given force to 80 cm, therefore it must have been compressed by another force and then released.

In this case, the instantanous speed is 0, since the block has just been released.

In the same instant we can stimate the free body diagram of forces by the next two equations:

$\sum_y{F}={F_N-W}=0\\\sum_x{F}={F_{spring}-F_{external}-F_{friction}}=ma$

For the y axis:

$F_N = W = mg = 3*9.8 = 29.4N$

To calculate the force of friction:

$F_{friction} = \mu_k F_N=0.4*29.4 = 11.76N$

Therefore for x axis:

${Kx-F_{external}-F_{friction}}=ma$

$a = \frac{130*0.8-88-11.76}{3} = \frac{104-88-11.76}{3}=\frac{4.24}{3}=1.41\frac{m}{s^2}$

7 0

3 years ago

How would planting trees and grass on a hillside help protect the land from these processes?

Arada [10]

Planting trees and grass on a hillside keeps the dirt and soil compacted so nothing fall.

I really do hope that this helps. ^_^

3 0

2 years ago

The ammeter below shows the current produced by a series of solar cells that contain zinc plates being used to power a simple se

nataly862011 [7]

The Ammeter shows: I = 15 A,
The circuit resistance is R = 0.2 Ohms.
By the Ohm`s Law:
R = V / I or:
V = I · R
V = 15 A · 0.2 Ohms
V = 3 V
Answer: C ) 3 V.

8 0

3 years ago