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jek_recluse [69]
3 years ago
13

A person driving a car suddenly applies the brakes. The car takes 4 s to come to rest while traveling 20 m at constant accelerat

ion. Can the speed of the car immediately before the brakes were applied be determined without first determining the car’s acceleration?
Physics
1 answer:
Zinaida [17]3 years ago
7 0

Answer:

Yes we can find the initial velocity of car without finding acceleration.

u = 10 m/s.

Explanation:

Given that

s=20 m

Car takes 4 s to come in rest.

We know that when acceleration is constant then we can apply motion equation

v=u+at        ----------1

s=ut+\dfrac{1}{2}at^2       ------2

From equation 1 and 2

s=ut+\dfrac{1}{2}t^2\left (\dfrac{v-u}{t} \right )

So we can say that

s= \left(\dfrac{v+u}{2}\right)t

Given that the velocity of car at final condition will be zero (v=0)

s= \left(\dfrac{0+u}{2}\right)t

s= \left(\dfrac{u}{2}\right)t

From the above equation we can find the initial velocity of car without finding the acceleration

20= \dfrac{u}{2}\times 4

u = 10 m/s

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A basketball is held over head at a height of 2.4 m. The ball is lobbed to a teammate at 8 m/s at an angle of 40'. If the ball i
cupoosta [38]

Explanation:

since both the teammates are of the same height, their height won't matter. Because now the basketball won't cover any vertical distance.

We have to calculate its range the horizontal distance covered by it when tossed from one teammate to the other.

range can be calculated by the formula :-

\boxed{\mathfrak{range =  \frac{  u  {}^{2}   \sin 2\theta }{g} }}

u is the velocity during its take off and \theta is the angle at which its thrown

Given that

  • u = 8m/ s
  • \theta = 40°

calculating range using the above formula

= \frac{ {8}^{2} \sin2(40)  }{10}

=  \frac{64 \times  \sin(80) }{10}

value of sin 80 = 0. 985

=  \frac{64 \times 0.985}{10}

=  \frac{63.027}{10}

= 6.3027

Hence,

\mathfrak { \blue{the \: teammate \: is \:  \red{\underline{6.3027 \: meters} }\: away } }

7 0
3 years ago
Could someone tell me if this is right or give me the answers so i can re write them! That would be so helpful:)
Ivahew [28]

Answer:

Those are all right

Explanation:

6 0
3 years ago
Read 2 more answers
A train moves moves from rest to a speed of 25 m/s in 30.0 sec . what is its acceleration
spayn [35]
A = Delta v/Delta t
Delta v = 25 - 0 = 25
Delta t = 30
25/30 = 5/6 = 1.66 repeating
7 0
3 years ago
Read 2 more answers
The pressure, p, of water (in pounds per square foot) at a depth of d feet below the surface is given by the formula p=15+15/33d
Viefleur [7K]
The pressure of the water on the diver is given in an expression written as:

<span>p=15+15/33d

where p is the pressure and d is the distance of the diver </span><span>below the surface.

The pressure is calculated as follows:

</span>p=15+15/33(100) = 15.00  pounds per square feet

Therefore, the correct answer is option A.
8 0
3 years ago
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The specific heat capacity of ethanol is 2440J/kg °C. How many joules of energy will be required to heat 150g ethanol to 35°C if
m_a_m_a [10]

Answer:

Required energy = 4758 J

Explanation:

Specific heat capacity of a material is the amount of energy required to raise the temperature of one kilogram (kg) of that material through one degree Celsius (°C).    

Given data :

Specific heat capacity = c = 2440 J/kg.°C

Mass = m = 150 g = 0.15 kg

Initial temperature = 22°C

Final temperature = 35°C

Change in Temperature = ΔT = 13°C

Energy = E = ?

Using the following formula and substituting the values, we get:

E = m × c × ΔT

E = 0.15 × 2440 × 13

E = 4758 J

8 0
3 years ago
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