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3 years ago

Electricity costs 10p per unit. How much will it cost Sam to use a 85W laptop and a 60W lamp for an hour?

1 answer:

6 0

The standard unit is KW/hr, = 1,000W/hr.
(85 + 60) = 145W.
You need to find its fraction of 1,000W., so (145/1000) = 0.145 KWH.
(0.145 x 10p) = 1.45p. per hr.

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An 7.9 kg crate is pulled 5.5 m up a 30∘ incline by a rope angled 19 ∘ above the incline. The tension in the rope is 140 N and t

dedylja [7]

Answer:

Wt= 0.73kJ, Wg=0.21kJ Wn= 0J

(B) Wf= 0.096kJ

Explanation:

See attachment below.

5 0

4 years ago

Is it safe to drive your 1600-kg car at speed 34 m/s around a level highway curve of radius 190 m if the effective coefficient o

adoni [48]

Answer:

It is unsafe

Explanation:

v = Velocity of car = 34 m/s

r = Radius of turn = 190 m

$\mu$ = Coefficient of static friction = 0.5

m = Mass of car = 1600 kg

g = Acceleration due to gravity = 9.81 m/s²

The centripetal force is given by

$F_c=m\frac{v^2}{r}\\\Rightarrow F_c=1600\frac{34^2}{190}\\\Rightarrow F_c=9734.73\ N$

The frictional force is given by

$F_f=\mu mg\\\Rightarrow F_f=0.5\times 1600\times 9.81\\\Rightarrow F_f=7848\ N$

If the centripetal force is greater than the frictional force then the car will slip which makes it unsafe.

Here, the centripetal force is greater than the frictional force which makes it unsafe to drive it at that speed.

4 0

3 years ago

When you approach a light source that in turn is moving towards you, your speed relative to the emitted light waves _____.?

Natalka [10]

This is a trick question:

The Doppler effect states that as you move closer to the source, the frequency of light(or sound/waves in general) increases, but technically the speed of light is always the same speed, even if you are moving at the speed of light.

Thus, the answer would be something along the lines of don't change.

7 0

4 years ago

Read 2 more answers

A block is being held in place on a frictionless surface. The block has a mass of 3.9 kg and is held in place on an incline of a

viva [34]

Answer:

block is being held in place on a frictionless surface. The block has a mass of 3.9 kg and is held in place on an incline of angle = 32° by a horizontal force F, as shown in the figure below.

Explanation:

7 0

3 years ago

A ship

Juli2301 [7.4K]

Answer:

The sea bed is 1125 m deep.

Explanation:

Speed

It's the rate of change of the distance (d) traveled by an object over time (t).

The speed can be calculated by the formula:

$\displaystyle v=\frac{d}{t}$

It's known the speed of sound in water is v=1500 m/s. A sound wave is sent to the sea bed and bounces back to the ship 1.5 seconds later.

That is the time the wave takes to travel twice the distance from the ship to the sea bed, thus the required distance uses half of that time or t=1.5/2 = 0.75 seconds.

Solving the equation for d:

d = v.t

d = 1500 m/s * 0.75 s

d = 1125 m

The sea bed is 1125 m deep.

4 0

3 years ago