8th grade physics (really easy!)?

Question

I don't want you to answer the question, just help me!
1. The speed of light is 3 x 10(to the) 8 (th power~ scientific notation) meters/sec. How long does it take light to travel the 149 x 10 (to the) 9 (th power) meters distance from the sun to the earth?

2. A driver starts his parked car and within 5 seconds reaches a velocity of 54 km/hr as he travels east. What is the acceleration?

thanx!

Answer 1

For (1) the equation you want is vt = d
That is, velocity multiplied by time is distance.
You know velocity and distance; solve for time.

For (2), the equation is v = at
That is, velocity is acceleration multiplied by time
You know velocity and time; solve for acceleration

You will probably have to convert km / hr to meters / second
There are 1000 m in a km and 3600 s in an hour

Answer 2

for 1.-

use the formula V=d/t (velocity is equal to displacement divide by time). You know the velocity and displacement, so rearrange for time. We get t=d/V. Now just plug in you values, so d is 149 x10 ^9 and V is 3 x10 ^8. You can solve that now.

for 2.- use the formula a= (Vf-Vi)/t. That's accelerationn is equal to the final velocity minus the initial velocity, all over the time. So first to convert from km/h to m/s, a simple trick is to simply divide by 3.6. So we get a value of 15 m/s. This is your final velocity. You know that the car starts from rest, so the initial time is 0 m/s. Finally you know the time over which the acceleratio took place, 5 s. So plug those values into you equation like this and solve:

a = (15 m/s-0m/s) / 5 s

(3 m/s^2)

Hope that helps!

Answer 3

look at the units to help you.
Speed is in meters per seconds (m / s)
Distance is in meters (m)
You wants to know the time in seconds (s)
m / (m / s) = s
distance / speed = time
149 E 9 / 3 E 8 = 497 seconds
497 seconds / 60 seconds per minutes = 8.3 minutes

2) To convert seconds to minutes, you have to know that there are 60 seconds in a minute. And you will need to know that there are 60 minutes in an hour. So there are 3600 seconds in an hour.
54 km/ hr = 54 km / 3600 seconds = 54 000 meters / 3600 seconds = 54/3.6 m/s
Acceleration is in m / s ^2 or meters per seconds per seconds
54 000 meters / 3600 seconds / 5 seconds = 3

The answer is 3 m/(s*s)

Answer 4

nicely, for question one, you may desire to describe WHY. Ex- The e book has no velocity, as a result we are able to end that the only stress performing on it is the stress through gravity, on condition that pronounced e book is extremely possibly on earth on the time at which that's resting on the table. (nonetheless it is not had to sound extremely so conceited). for 2, nicely i think your answer is precise. possibly you mandatory to specify the direction of the stress the wall is exerting. Ex- The cart did no longer flow because of the fact the wall became exerting an equivalent and opposite stress decrease back on the cart. Ex (seen) - stress Alexa --------> <-------- stress Wall

Answer 5

im in 8th grade too! :)