Physics problem help

[scota]

Can someone PLEASE help me with the following physics problem:

A 27 pound meteorite struck a car, leaving a dent 23 cm deep in the trunk. If the meteorite struck the car with a speed of 630 m/s, what was the magnitude of its deceleration, assuming it to be constant?

I don't even know what formula to use . Thanks.

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[51487]

Can someone PLEASE help me with the following physics problem:

A 27 pound meteorite struck a car, leaving a dent 23 cm deep in the trunk. If the meteorite struck the car with a speed of 630 m/s, what was the magnitude of its deceleration, assuming it to be constant?

I don't even know what formula to use . Thanks.

use the kinematics formula w/o time in it? right? vf^2=vi^2 + 2ad, is it?

 

[scota]

That formula worked for another problem! Thanks...

 

[scota]

Thanks! Answer was 826826 by the way !

 

[liverotcod]

Thanks! Answer was 826826 by the way !

What units?

 

[leechy]

What units?

Yeah, I'd like to know as well - what units?????

Deductions and red ink galore.

 

[Phased]

What units? The speed they give you is 630 m/s and the distance it took to slow down is 23 cm (0.23 m), that's all you're working with really, it's pretty much known that it'll be in m^2/s^2 since they want you to find the deceleration (acceleration).

0 = 630^2 + 2(a)(0.23)
a=-862826

But since all you want is the 'deceleration' (negative acceleration) the answer is 862,826 m^2/s^2


ALTHOUGH there is another approach to this problem, using energy.

Since the meteor is coming down at a velocity 630 m/s, it has kinetic energy and gravitational potential energy. At the point where it hits the car, it has only kinetic energy (relative to the car). The meteor hits the car, and dent's it 23 cm to the point where the meteor no longer is moving - has no kinetic energy. That means, all the k.e. that the meteor had went into overcoming the car's trunk and denting it - and since work is really a force times a distance the relationship can be described as:

(1/2)*(m)*(v^2) = F*d

which is pretty much reduced, since F = m * (-a) since it's opposing acceleration, it's (with the - removed since we're looking for deceleration)
(1/2)*(v^2) = a*d
0.5 * 630^2 = a (0.23)

same damn thing

 

[Wiggy73]

What units? The speed they give you is 630 m/s and the distance it took to slow down is 23 cm (0.23 m), that's all you're working with really, it's pretty much known that it'll be in m^2/s^2 since they want you to find the deceleration (acceleration).

0 = 630^2 + 2(a)(0.23)
a=-862826

But since all you want is the 'deceleration' (negative acceleration) the answer is 862,826 m^2/s^2


ALTHOUGH there is another approach to this problem, using energy.

Since the meteor is coming down at a velocity 630 m/s, it has kinetic energy and gravitational potential energy. At the point where it hits the car, it has only kinetic energy (relative to the car). The meteor hits the car, and dent's it 23 cm to the point where the meteor no longer is moving - has no kinetic energy. That means, all the k.e. that the meteor had went into overcoming the car's trunk and denting it - and since work is really a force times a distance the relationship can be described as:

(1/2)*(m)*(v^2) = F*d

which is pretty much reduced, since F = m * (-a) since it's opposing acceleration, it's (with the - removed since we're looking for deceleration)
(1/2)*(v^2) = a*d
0.5 * 630^2 = a (0.23)

same damn thing

Nice analysis - except acceleration is in m/s^2, not m^2/s^2. Good point about the two methods, though!

 

[Jason110]

What units?

0 = 630^2 + 2(a)(0.23)
a=-862826

But since all you want is the 'deceleration' (negative acceleration) the answer is 862,826 m^2/s^2

It should be m/s^2 NOT what units you have there. Acceleration is given as m/s^2 ... and the units above work out. Where's that red pen?

Jason

 

[scota]

. Thanks for the help everybody. I'll be sure to take advantage of people's willingness to help .

 

[Phased]

It should be m/s^2 NOT what units you have there. Acceleration is given as m/s^2 ... and the units above work out. Where's that red pen?

Jason

lol. dude, I just got PHAZED. Haha. My mind was on the energy approach, as in m/s^2 * m. You buying it????

Ah f it, who cares I got the number right.

d =d
v = d / t
a = v / t = ( d / t ) / t = d/t^2