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andre [41]
3 years ago
6

A train is travelling towards the station on a straight track. It is a certain distance from the station when the engineer appli

es the brakes. Initially, the train is moving at 50 m/s and slows down at 2.5 m/s^2. If the train stops at the station, how far before the station did the engineer apply the brake?
Physics
1 answer:
AleksandrR [38]3 years ago
4 0

Answer:

500 m

Explanation:

t = Time taken

u = Initial velocity = 50 m/s

v = Final velocity = 0

s = Displacement

a = Acceleration = -2.5 m/s²

Equation of motion

v=u+at\\\Rightarrow 0=50-2.5\times t\\\Rightarrow \frac{-50}{-2.5}=t\\\Rightarrow t=20\ s

Time taken by the train to stop is 20 seconds

s=ut+\frac{1}{2}at^2\\\Rightarrow s=50\times 20+\frac{1}{2}\times -2.5\times 20^2\\\Rightarrow s=500\ m

∴ The engineer applied the brakes 500 m from the station

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A balloon contains helium with a mass of 0.00296 g. What is the volume of helium in the balloon? (Note: Helium’s density is 0.00
Over [174]

Answer:

178 cm3

Explanation:

From definition of density, it is mass per unit volume of an object, expressed as density=mass/volume and making volume the subject of the above formula we have volume= mass/density and substituting 0.00296 g for mass and 0.00001663 g/cm3 for density then we have

Volume=0.00296/0.00001663

Volume is approximately 178 cm3

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Free electrons may be transferred between bodies by:
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3 years ago
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Calculate the velocity of an apple that falls freely from rest and drops for 3.5 seconds.
padilas [110]

Answer:

initial velocity(u)=0

time(t)=3.5sec

acceleration (a)=9.8m/s²

final velocity (v)=?

Explanation:

we have

v=u+at=0+9.8×3.5=34.3m/s

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3 years ago
Kuiper Belt objects are composed of which substances? Select all that apply.
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8 0
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A ball thrown horizontally at 12.6 m/s from the roof of a building lands 20.0 m from the base of the building
S_A_V [24]

Answer:

1.59 seconds

12.3 meters

but if you are wise you will read the entire answer.

Explanation:

This is a good question -- if not a bit unusual. You should try and understand the details. It will come in handy.

Time

<u>Given</u>

a = 0 This is the critical point. There is no horizontal acceleration.

d = 20 m

v = 12.6 m/s

<u>Formula</u>

d = vi * t + 1/2at^2

<u>Solution</u>

Since the acceleration is 0, the formula reduces to

d = vi * t

20 = 12.6 * t

t = 20 / 12.6

t = 1.59 seconds.

It takes 1.59 seconds to hit the ground

Height of the building

<u>Givens</u>

t = 1.59 sec

vi = 0     Another critical point. The beginning speed vertically is 0

a = 9.8 m/s^2   The acceleration is vertical.

<u>Formula</u>

d = vi*t + 1/2 a t^2

<u>Solution</u>

d = 1/2 a*t^2

d = 1/2 * 9.8 * 1.59^2

d = 12.3 meters.

The two vi's are not to be confused. The horizontal vi is a number other other 0 (in this case 12.6 m/s horizontally)

The other vi is a vertical speed. It is 0.

7 0
3 years ago
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