How many cookies does it take to reach the moon???!!

A train 471 m long is moving on a straight track with a speed of 75.1 km/h. The engineer applies the brakes at a crossing, and l

hram777 [196]

Answer:

$t = 37.6 s$

Explanation:

As we know that train is initially moving with the speed

$v_i = 75.1 km/h$

now we know that

$v_i = 20.86 m/s$

now the final speed of the train when it crossed the crossing

$v_f = 15 km/h$

$v_f = 4.17 m/s$

now we can use kinematics here

$v_f^2 - v_i^2 = 2 a d$

$4.17^2 - 20.86^2 = 2 a(471)$

$a = -0.44 m/s^2$

Now the time to cross that junction is given as

$v_f - v_i = at$

$4.17 - 20.86 = a(-0.44)$

$t = 37.6 s$

4 0

2 years ago

Sandy is whirling a ball attached to a string in a horizontal circle over his head. If Sandy doubles the speed of the ball, what

jeka57 [31]

The tension in the string B) It quadruples.

Explanation:

The ball is in uniform circular motion in a horizontal circle, so the tension in the string is providing the centripetal force that keeps the ball in circular motion. So we can write:

$T= m\frac{v^2}{r}$

where:

T is the tension in the string

m is the mass of the ball

v is the speed of the ball

r is the radius of the circle (the lenght of the string)

In this problem, we are told that the speed of the ball is doubled, so

v' = 2v

Substituting into the previous equation, we find the new tension in the string:

$T' = m \frac{(2v)^2}{r}=4(m\frac{v^2}{r})=4T$

Therefore, the tension in the string will quadruple.

Learn more about circular motion:

brainly.com/question/2562955

brainly.com/question/6372960

#LearnwithBrainly

6 0

3 years ago

Heat transfer between two substances is affected by specific heat and the

IgorLugansk [536]

The correct answer is D. Amount of time and area of physical contact between the substances.

Explanation:

Heat transfer refers to the flow of thermal energy or heat between two or more objects. This process involves multiple factors and implies heat from the hottest object goes to the coldest one until there is an equilibrium. To begin, heat transfer depends on the amount of thermal energy in the objects because objects must have a different amount of thermal energy for heat to flow.

Besides this, the amount of energy that flows depends on the time and the contact between the substances of objects. Indeed, objects need to be in contact or close to each other for heat to transfer, and the time needs to be enough for the process to occur. For example, if you place a pot over the fire just for a few seconds it is likely the heat transferred is minimal, which does not occur if you leave the pot more time. At the same time if the pot is in close contact with fire more heat will be transferred.-

6 0

3 years ago

A rural mail carrier logged the mileage on the odometer at the start of the mail route as 31,500 miles. After 6.5 hours, the car

dusya [7]

Answer: $32.77\ mi/hr$

Explanation:

Given

Initially Reading on the odometer is $31,500\ miles$

Final reading on the odometer is $31,713\ miles$

Time taken is $t=6.5\ hr$

average velocity $=\dfrac{\text{Displacement}}{\text{time}}$

$v_{avg}=\dfrac{31713-31500}{6.5}$

$v_{avg}=\dfrac{213}{6.5}$

$v_{avg}=32.77\ mi/hr$

Thus the average velocity of mail truck is $32.77\ mi/hr$

8 0

3 years ago

PLS HEP WILL GIVE BRAINLIEST TO FIRST ANSWER SCIENCEE!!

MAVERICK [17]

Answer:

Claim: The heart pumps more blood throughout the body when one exercises because exercise takes a lot of energy from the body.

Evidence: Heart rate went from 80 bpm to 120 bpm

Reasoning: Doing exercise takes a lot of energy to do, causing the circulatory system to have to work harder and pump more blood throughout the body in order to allow someone to be able to do a task that involves so much movement and energy.

Explanation:

3 0

2 years ago