Ask question

Ask question

All categories

3 years ago

12

John runs 120 meters in 10 seconds and then runs back to where he started in another 10 seconds. Which statement is true? Rememb

er: speed and velocity mean the same thing. Acceleration is a change is speed over a change in time.

1 answer:

atroni [7]3 years ago

4 0

Answer:

B

Explanation:

<em>A. His speed is 0 m/s </em>

<em>B. His velocity is 12 m/s </em>

<em>C. His velocity is 0 m/s </em>

<em>D. His acceleration is 12 m/s</em>

Total distance traveled by John = 120 + 120 = 240 meters

Total time taken by John to cover the distance = 10 + 10 = 20 s

<em>Average speed of John = total distance traveled/total time taken</em>

= 240/20 = 12 m/s

Hence, the average speed/velocity of John throughout the journey is 12 m/s.

The correct option is B.

You might be interested in

A constant force of 45 N directed at angle θ to the horizontal pulls a crate of weight 100 N from one end of a room to another a

Rasek [7]

Answer:

$W=173.48J$

Explanation:

information we know:

Total force: $F=45N$

Weight: $w=100N$

distance: $4m$

vertical component of the force: $F_{y}=12N$

-------------

In this case we need the formulas to calculate the components of the force (because to calculate the work we need the horizontal component of the force).

horizontal component: $F_{x}=Fcos\theta$

vertical component: $F_{y}=Fsen\theta$

but from the given information we know that $F_{y}=12N$

so, equation these two $F_{y}=Fsen\theta$ and $F_{y}=12N$

$Fsen\theta =12N$

and we know the force $F=45N$ , thus:

$45sen\theta=12$

now we clear for $\theta$

$sen\theta =12/45\\\theta=sin^{-1}(12/45)\\\theta =15.466$

the angle to the horizontal is 15.466°, with this information we can calculate the horizontal component of the force:

$F_{x}=Fcos\theta$

$F_{x}=45cos(15.466)\\F_{x}=43.37N$

whith this horizontal component we calculate the work to move the crate a distance of 4 m:

$W=F_{x}*D\\W=(43.37N)(4m)\\W=173.48J$

the work done is W=173.48J

7 0

3 years ago

The coefficient of linear expansion of copper is 17 x 10^-6 K-1. A block of copper 30 cm wide, 45 cm long, and 10 cm thick is he

schepotkina [342]

Answer:

The change in volume is $6.885\times 10^{- 5}\$

Solution:

As per the question:

Coefficient of linear expansion of Copper, $\alpha = 17\times 10^{- 6}\ K^{- 1}$

Initial Temperature, T = $0^{\circ}$ = 273 K

Final Temperature, T' = $100^{\circ}$ = 273 + 100 = 373 K

Now,

Initial Volume of the block, V = $30\times 45\times 10\times 10^{- 6}\ m^{3} = 0.0135\ m^{3}$

$V' = V(1 + \gamma \Delta T)$

$\gamma = 3\alpha$

$V' = V(1 + 3\alpha \Delta T)$

where

V' = Final volume

$V' - V= 0.0135\times 17\times 10^{- 6} \times (T' - T))$

$\Delta V= 0.0135\times 3\times 17\times 10^{- 6} \times (373 - 273)) = 6.885\times 10^{- 5}\$

7 0

3 years ago

if the distance of separation begin two objects is doubled, is the gravitational force between the objects increased or decrease

SashulF [63]

Answer:

force is decreased by a factor of 4.

Explanation:

According to the Newton's law of gravitation, the force of gravitation between the two object is inversely proportional to the square of distance between them. Now the distance is doubled, so the force between the two objects becomes one forth.

Force is decreased by a factor or 4.

7 0

3 years ago

Please......... I need desperate help

PIT_PIT [208]

' A ' is one crest of the wave. After every wavelength, there's another one.

' B ' . . . the vertical arrow under B shows the amplitude of the wave

' C ' is one trough of the wave. After every wavelength, there's another one.

' D ' . . . the horizontal arrow over D shows the wavelength.

3 0

3 years ago

A hockey puck is traveling to the left with a velocity of v=10 when it is struck by the hockey stick

Lera25 [3.4K]

We have to calculate the impulse of a hockey puck.
Imp = m * ( v 1 - v 2 ) = m * Δ v
v 1 = - 10 i m/s,
v 2 = ( 20 * cos 40° ) i + ( 20 * sin 40° ) j =
= ( 20 * 0.766 ) i + ( 20 * 0.64278 ) j = ( 15.32 i + 12.855 j ) m/s
Δ v = ( 15.32 i + 12.855 j ) - ( - 10 i ) =
= 15.32 i + 12.855 j + 10 i = 25.32 i + 12.855 j
| Δv | = √ ( 25.32² + 12.855²) = √806.35 = 28.4 m/s
Imp = 0.2 kg * 28.4 m/s = 5.68 N-s
Answer: D ) 5.68 N-s.

4 0

3 years ago