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rusak2 [61]
3 years ago
7

A school bus moves past a parked car at a speed of 30 km/hr. Which of the following BEST describes the observation made by a pas

senger on the bus? A.The car appears to be moving 15 km/hr in the same direction as the bus.
B.The car appears to be moving 30 km/hr in the same direction as the bus.
C.The car appears to be moving 30 km/hr in the opposite direction of the bus.
D.The car appears to be moving 15 km/hr in the opposite direction of the bus.
Physics
1 answer:
ddd [48]3 years ago
8 0

Answer:

C.The car appears to be moving 30 km/hr in the opposite direction of the bus.

Explanation:

There are two reference systems involved in this situation:

- Reference system S: this is the reference system where velocities are measured with respect to the ground. In this reference system, the car is parked, so its velocity is v=0

- Reference system S': this is the reference system moving with the bus. This reference system is moving with a velocity of v_0 = +30 km/h with respect to the reference system S

Calling v' the velocity of the car in the reference system S', we have:

v=v_0 +v'

From which

v'=v-v_0 = 0-(+30 km/h)=-30 km/h

and the negative sign means that a passanger in the bus observes the car moving in the opposite direction.

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S=S_{o}+v_{o}t+ \frac{at^2}{2} \\ 20= \frac{10t^2}{2} \\ t=2s
 
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\Delta v=  \frac{\Delta S}{\Delta t}  \\ v_x= \frac{36}{2}  \\ \boxed {v_{x}=18m/s}


B)
 
     Using the Velocity Hourly Equation in vertical direction, we have:

v_{y}=v_{y_{o}}+gt \\ v_{y}=10\times2 \\ \boxed {v_{y}=20m/s}
  
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cos(\theta) =\frac{v_{x}}{v_{y}}  \\ cos(\theta) = \frac{18}{20}  \\ cos(\theta) =0.9 \\ arccos(0.9)=\theta \\ \boxed {\theta \approx 25.84}


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With fuel prices for combustible engine automobiles increasing, researchers and manufacturers have given more attention to the c
Alinara [238K]

Answer:

Then the difference of weight between the two cars are:

Δw = 14210 - 5292 = 8918 N

Explanation:

An object's weigh due to the gravitational attraction force of the earth is:

w = mg

            Where: m is the object's mass

                         g is the  gravitational acceleration in the surface earth

                         g = 9.8 m/s2

The the ultralight car's weight is:

w_{uc} = (540)(9.8)

w_{uc} = 5292 N

And the Honda Accord's weight is:

w_{HA} = (1450)(9.8)

w_{HA} = 14210 N

Then the difference of weight between the two cars are:

Δw = 14210 - 5292 = 8918 N

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3 years ago
A person jogs for 4.0 km in 32 mins,then 2.0km in 22mins,and finallu 1.0 km in 16 mins.whqt is the joggers average speed in km p
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Average speed = (total distance covered) / (time to cover the distance)

total distance covered = (4km + 2km + 1km) = 7 km

time to cover the distance = (32min + 22min + 16min) = 70 min

Average speed = (7 km) / (70 min)

Average speed = 0.1 km/minute

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