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3 years ago

13

A motorcyclist sees a branch in the road, and hits the brakes, slowing down at -6.42 m/s^2. If it takes him 2.85 s to stop, what

was his starting velocity?

1 answer:

Alex_Xolod [135]3 years ago

3 0

Answer:

his starting velocity was 18.297 ms⁻¹

Explanation:

v = u + at .................. (1)

Where

Final Velocity (v) = 0 ms⁻¹

Initial velocity (u) = ?

Acceleration (deceleration) (a) = -6.42 ms⁻²

time (t) = 2.85 s

Substituting all parameters into equation (1)

0 = u + (-6.42)2.85

0 = u + (-18.297)

0 = u - 18.297

18.297 = u

∴ the initial velocity was 18.297 ms⁻¹

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A student is studying the potential energy change of a 50 kg object raised 110 km above Earth's surface. What will be the percen

Law Incorporation [45]

Answer:

The percentage error is given by 99.9 %

Explanation:

Given:

Mass of object $m = 50$ kg

Height $h = 110$ km

From the formula of potential energy,

$U = mgh$

Where $g = 9.8 \frac{m}{s}$

$U = 50\times 9.8 \times 110000$

Here true value of potential energy,

$U = 50 \times 9.8 \times 11 \times 10^{4}$

Approximate value of student,

$U = 50 \times 9.8 \times 110$

Absolute error is given by

= true value - approximate value

= $50 \times 9.8 \times 11 \times 10^{4} - 50 \times 9.8 \times 110$

= $53846100$

Hence percentage error,

$= \frac{53846100}{50 \times 9.8 \times 11 \times 10^{4} }$

$= 0.999 \times 100$ %

$= 99.9$ %

Therefore, the percentage error is given by 99.9 %

7 0

3 years ago

A 100-mm pipe is used to transfer oil from a reservoir to a 100- liter tank. It takes 45 minutes to fill the tank with oil that

Firlakuza [10]

Explanation:

Given that,

Diameter =100 mm

Volume = 100 liter

Time = 45 min

Viscosity = 0.005 Pas

Density = 900 kg/m³

(a). We need to calculate the volume flow rate of oil

Using formula of flow rate

$q=\dfrac{V}{t}$

Put the value into the formula

$Q=\dfrac{0.1}{2700}$

$Q=3.7\times10^{-5}\ m^3/s$

The volume flow rate of oil is $3.7\times10^{-5}\ m^3/s$

(b). We need to calculate the mean velocity in the pipe

Using formula of mean velocity

$v=\dfrac{Q}{A}$

$v=\dfrac{Q}{\dfrac{\pi}{4}\times d^2}$

Put the value into the formula

$v=\dfrac{3.7\times10^{-5}}{\dfrac{\pi}{4}\times(100\times10^{-3})^2}$

$v=4.7\times10^{-3}\ m/s$

The mean velocity in the pipe is $4.7\times10^{-3}\ m/s$ .

(c). We need to calculate the Reynolds number

Using formula of the Reynolds number

$R_{e}=\dfrac{\rho v d}{\mu}$

Put the value in to the formula

$R_{e}=\dfrac{900\times4.7\times10^{-3}\times100\times10^{-3}}{0.005}$

$R_{e}=84.6$

The Reynolds number is 84.6.

(d). We need to calculate the maximum velocity in the pipe

Using formula of maximum velocity

$V_{max}=2v_{avg}$

Put the value into the formula

$v_{max}=2\times4.7\times10^{-3}$

$v_{max}=9.4\times10^{-3}\ m/s$

The maximum velocity in the pipe is $9.4\times10^{-3}\ m/s$

Hence, This is the required solution

7 0

4 years ago

3. What is the acceleration of a car at rest that stays at rest over 10 seconds?

Yuliya22 [10]

Answer:

a.

Explanation:

Use accleration formula,

$a = \frac{v _{f} - v _{i}}{t}$

The initial velocity and final velocity is at zero. and t=10

So we got

$\frac{0}{10} = 0$

so

$a = 0$

a is the answer

8 0

2 years ago

What is the acceleration of an 800kg car that has a force of 2400N?<br> A= F/M

dangina [55]

You habe already the formula, what's wrong then? it's simple

A = F/M

A = 2400/800

A = 24/8

A = 3 m/s²

6 0

3 years ago

wo kids are on a seesaw. The one on the left has a mass of 75 kg and is sitting 1.5 m from the pivot point. The one on the right

Anastaziya [24]

Answer:

4.5 Nm (Anticlockwise)

Explanation:

Let the 75 kg kid is sitting at the left end and the 60 kg kid is sitting on the right end.

Anticlockwise Torque = 75 x 1.5 = 112.5 Nm

clockwise Torque = 60 x 1.8 = 108 Nm

Net torque = Anticlockwise torque - clockwise torque

Net Torque = 112.5 - 108 = 4.5 Nm (Anticlockwise)

5 0

3 years ago