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3 years ago

7. A car is travelling along a road at 30 ms when a pedestrian steps into the road 55 m ahead. The

Physics

1 answer:

trasher [3.6K]3 years ago

6 0

Answer: Car collide with man

Explanation:

Given

Speed of car is $u=30\ m/s$

Distance of the man from the car is $s=55\ m$

Reaction time $t_r=0.5\ s$

Rate of deceleration $a_d=-10\ m/s^2$

Distance traveled in the reaction time $d_o=30\times 0.5=15\ m$

Net effective distance to cover $d=55-15=40\ m$

Distance required to stop the car

$\Rightarrow v^2-30^2=2(-10)(s)\\\Rightarrow 0-900=-20s\\\Rightarrow s=45\ m$

Require distance is more than that of net effective distance. Hence, car collides with the man.

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?a wire is stretched 30% what is the percentage change in resistance

Marat540 [252]

Answer:

The percentage change in resistance of the wire is 69%.

Explanation:

Resistance of a wire can be determined by,

R = (ρl) ÷ A

Where R is its resistance, l is the length of the wire, A its cross sectional area and ρ its resistivity.

When the wire is stretched, its length and area changes but its volume and resistivity remains constant.

$l_{o}$ = 1.3l, and $A_{o}$ = $\frac{A}{1.3}$

So that;

$R_{o}$ = (ρ $l_{o}$ ) ÷ $A_{o}$ = (ρ × 1.3l) ÷ ( $\frac{A}{1.3}$ )

= (1.3lρ) ÷ ( $\frac{A}{1.3}$ )

= $(1.3)^{2}$ × [(ρl) ÷ A]

= 1.69R (∵ R = (ρl) ÷ A)

$R_{o}$ = 1.69R

Where $R_{o}$ is the new resistance, $l_{o}$ is the new length, and $A_{o}$ is the new area after stretching the wire.

The change in resistance of the wire = $R_{o}$ - R

= 1.69R - 1R

= 0.69R

The percentage change in resistance = $\frac{0.69R}{R}$ × 100

= 0.69 × 100

= 69%

The percentage change in resistance of the wire is 69%.

3 0

3 years ago

Does anyone understand This question if you do can you tell me the answer

leonid [27]

Answer:

50N increasing

Explanation:

it looks like we want the net force. this is the sum of all forces acting on the object. here the problem is extremely simplified and we are even given the values of force. this looks like the rocket is producing an upward force of 160 newtons. it also looks like maybe weight (gravity) and drag (air resistance) are producing downward force against the rocket. we can say those would be subtracting from the amount of upwards force. so 160-40-70=50N. since the force is positive that means we will still have a magnitude of force vector that points upward and so we will increase.

6 0

3 years ago

How do scientists know when a new species is created ?

noname [10]

Because they have special tool's that help them find out

7 0

3 years ago

A rare butterfly (0.01 kg) is slowly flapping its wings and moving across a road. An unsuspecting driver in a large car (1000 kg

aliya0001 [1]

Both the butterfly and the large car will have equal forces but in opposite direction.

<h3>Newton's third law of motion</h3>

Newton's third law of motion states that action and reaction are equal and opposite. That is, the force exerted on an object is equal to the reaction experienced by the object.

Fa = - Fb

where;

Fa is the force exerted by the large car
Fb is the force of the butterfly

Thus, both the butterfly and the large car will have equal forces but in opposite direction.

Learn more about Newton's third law of motion here: brainly.com/question/25998091

#SPJ1

8 0

2 years ago

Need help with these physic questions!

gtnhenbr [62]

Explanation:

Given: Δd = 4 + 2 + 1 = 7km, Δt = 32 + 22 + 16 = 70mins

Required: V

Equation: V = Δd/Δt

Solution: V = 7/70

= 0.1km/min

6 0

3 years ago