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Nostrana [21]
3 years ago
8

Many kayaks are made of plastic and other composite materials that are denser than water. How are such kayaks able to float in w

ater?
Physics
1 answer:
KIM [24]3 years ago
5 0
Beacuse they are built different and materials are put in the right spots
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Use the work—energy theorem to solve each of these problems. You can use Newton's laws to check your answers. Neglect air resist
andreyandreev [35.5K]

Answer:

a) It is moving at 43.15\frac{m}{s^{2}} when reaches the ground.

b) It is moving at 101.44\frac{m}{s^{2}} when reaches the ground.

Explanation:

Work energy theorem states that the total work on a body is equal its change in kinetic energy, this is:

W=K_f-K_i (1)

with W the total work, Ki the initial kinetic energy and Kf the final kinetic energy. Kinetic energy is defined as:

K=\frac{mv^2}{2} (2)

with m the mass and v the velocity.

Using (2) on (1):

W=\frac{mv_f^2}{2}-\frac{mv_i^2}{2} (3)

In both cases the total work while the objects are in the air is the work gravity field does on them. Work is force times the displacement, so in our case is weight (w=mg) of the object times displacement (d):

W=Fd=wd=mgd (4)

Using (4) on (3):

mgd=\frac{mv_f^2}{2}-\frac{mv_i^2}{2} (5)

That's the equation we're going to use on a) and b).

a) Because the branch started form rest initial velocity (vi) is equal zero, using this and solving (5) for final velocity:

v_f=\sqrt{\frac{2mgd}{m}}=\sqrt{2gd}=\sqrt{2*9.8*95}

v_f=43.15\frac{m}{s^{2}}

b) In this case the final velocity of the boulder is instantly zero when it reaches its maximum height, another important thing to note is that in this case work is negative because weight is opposing boulder movement, so we should use -mgd:

-mgd=-\frac{mv_i^2}{2}

Solving for initial velocity (when the boulder left the volcano):

v_i=\sqrt{\frac{2mgd}{m}}=\sqrt{2gd}=\sqrt{2*9.8*525}

v_i=101.44 \frac{m}{s^{2}}

3 0
3 years ago
How much is the plane's acceleration while breaking if it takes 15 s for its velocity
Marizza181 [45]

Answer:

A. 4.67 m/s²

Explanation:

u = 145 m/s

v = 75 m/s

t = 15 s

a = v - u / t

= 145 - 75 / 15

= 4.67 m/s²

Hope this helped...

7 0
3 years ago
kristine speeds past a parked police car at 32 m/s. The police car starts from rest with a uniform acceleration of 2.5 m/s^2. Ho
Digiron [165]

32 = 0 \times t +  \frac{1}{2} \times 2.5 \times t^{2}     \\  32 = 0 + 1.25 \times t {}^{2}  \\ 32 = 1.25t {}^{2}   \\   \frac{32}{1.25}  =  \frac{1.25t {}^{2} }{1.25}  \\ t {}^{2}  = 25.6 \\  \sqrt{t {}^{2} }  =  \sqrt{25.6}  \\ t = 5.1seconds \\

7 0
2 years ago
During a race, a runner runs at a speed of 6 m/s. 2 seconds later, she is running at a speed of 10 m/s. What is the runner’s acc
Lapatulllka [165]
Let's calculate the average acceleration. It is the rate of changing speeds. Hence, we need to calculate the difference of speeds. 10-6=4 m/s. The rate is now \frac{4m/s}{2s} =2m/s^2.
In general, the formula for the mean acceleration between two times 1 and 2 is given by:
\frac{u_2-u_1}{T} where v1 and v2 are the speeds at the respective points and T is the time interval between them.
5 0
3 years ago
which of the following is the correct si unit to use in measuring the mass of a boulder a. tons b. kilograms c. ounces d. pounds
Salsk061 [2.6K]
B. kilograms iuyiuiuhikj
7 0
3 years ago
Read 2 more answers
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