Calculating Car Mass with Constant Speed on a Bridge

[Lee80]

If a car is traveling towards a bridge at a constant speed of 20ms-1. The bridge takes 30s to cross entirely. The car creates a force of 3000N. Calculate the mass of the car when it is on the bridge.


a=(v2-v1)/t
F=ma

I figured that a = 0 due to the fact that the car is traveling at constant speed.
If a = 0 then isn't it impossible for the car to create a force of 3000N? I am very confused?

 

[adjacent]

If a car is traveling towards a bridge at a constant speed of 20ms-1. The bridge takes 30s to cross entirely. The car creates a force of 3000N. Calculate the mass of the car when it is on the bridge.a=(v2-v1)/t
F=ma

I figured that a = 0 due to the fact that the car is traveling at constant speed.
If a = 0 then isn't it impossible for the car to create a force of 3000N? I am very confused?

First,the speed is expressed as m/s not ms-1.
When does the car create a force of 3000N?On the start of bridge?

Edit:Oh I forgot.Welcome to PF

 

[NascentOxygen]

If a car is traveling towards a bridge at a constant speed of 20ms-1. The bridge takes 30s to cross entirely. The car creates a force of 3000N. Calculate the mass of the car when it is on the bridge.


a=(v2-v1)/t
F=ma

I figured that a = 0 due to the fact that the car is traveling at constant speed.
If a = 0 then isn't it impossible for the car to create a force of 3000N? I am very confused?

Hi Lee80! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

I'm a little confused by the question, too. Perhaps the bridge is curved, maybe semicircular? It is not clear whether this 3000N is a vector sum of multiple forces, including also that force known as the vehicle's weight.

Are you sure you have quoted the question details in full?

 

[Lee80]

Thanks for the welcome! :)
I have written the question exactly the way it is on the page including the ms-1, which i know is supposed to be superscript but isn't it interchangable with m/s? Anyway the only extra info given was a second part to the question which asks "The bridge can support a mass of 5 tonne or less safely. Is it safe for the car to travel across the bridge?"
I don't think the question is correct? I think it needs more info. The question is supposed to be aimed at year 11 physics.

 

[NascentOxygen]

I have written the question exactly the way it is on the page

Pity, because it sounded like the basis of a good question: "If the bridge is of level height but curves around the coastline in a semicircular arc, determine that radius of curvature, and the length of the bridge ..."

including the ms-1, which i know is supposed to be superscript but isn't it interchangable with m/s?

Sure is.

Anyway the only extra info given was a second part to the question which asks "The bridge can support a mass of 5 tonne or less safely. Is it safe for the car to travel across the bridge?"
I don't think the question is correct? I think it needs more info. The question is supposed to be aimed at year 11 physics.

There is either too much information provided, or else not enough. But something's amiss.

 

[SammyS]

Thanks for the welcome! :)
I have written the question exactly the way it is on the page including the ms-1, which i know is supposed to be superscript but isn't it interchangeable with m/s?

Yes, if the -1 is a superscript then they're interchangeable.

Use the X² icon above the message box for superscripts.


m/s is ms^-1 .