Simple Physics

Tommy B

Tommy B

Tommy B

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1. A car of mass 850 kg accelerates at 2 m/s2. What resultant force is accelerating it?

HOW THE **** do you work this out. Excuse me for being impatient but I've lost it. I don't understand how the hell you get the speed into N. You can use W=MG to get the 850kg into N, bu what about the friggin speed. I hate physics.

Cheers :D
 
1. A car of mass 850 kg accelerates at 2 m/s2. What resultant force is accelerating it?

OK. So I've got F=MA, 850*2 = 1700N
I've also got 850*9.8 = 8500N

So Square root of those two added togethor?
 
Because I need to work out the resultant force so both the forces need to be in N.

Please can someone confirm?
 
Tommy B said:
Because I need to work out the resultant force so both the forces need to be in N.

Please can someone confirm?
Click to expand...

But the only resultant force is going ----->
The force downwards is being balanced by whatever the car is driving on.
 
This always happens to me. I try and be too complicated. Why the hell do I have to make everything so complicated. Grrr.

Thanks to those who helped!
 
The forces acting on the car are the engine pushing it sideways, its own weight pulling it downwards, and a resistance force from the road pushing it upwards. Clearly the resistance force must balance the weight, or the car would move upwards or downwards! So on the 'F' side of the equation you only need to take the force of the car's engine into account. On the 'ma' side you have the mass of the car (850kg) times the acceleration (2m/s/s) which gives you 1700 kg m/s/s, and 1 kg m/s/s is another way of saying 1 N. So the force pushing the car sideways is 1700 N.
 
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Tommy B said:
You always add components to get the resultant force though?
Click to expand...


the 2 components, i.e. the acceleration of the car and the weight of the car acting downwards are at 90 degrees to eachother so there would be no resultant anywya.

Also, there is no force in the vertical direction because the car isnt moving up or down, therefore, the weight of the car is being equally opposed by the road, you only have to worry about the horizontal direction, which has already been explained is simply F= ma.
 
I've been doing Physics since about 7am. Is it possible my brain has just turned off.

Seriously I'm now stuck on part two.

Mass of car = 1.3x10^3 kg

b) When the accelerating car reaches a speed of 2.2ms-1, the total force opposing the motion of the car is 410N. Calculate the driving force provided by the wheels.
 
You also mentioned speed. Since we aren't dealing with directions, we'll use velocity interchangeably.

If you think of a velocity/time graph, you have constant accelleration, so the graph will look like a triangle, with time along the bottom, and with a gradient of 2m/s^2. So v = at = 2t.

Displacement (s)
Assuming starting at zero speed, think about the velocity time graph again - time along the bottom with velocity up the side. The graph looks like a triangle, with the area under the graph representing the distance travelled, sometimes called displacement or separation.
s = 1/2 vt
 
Arcade Fire said:
Same as before - you need to use F=ma. In this case on the 'F' side of the equation you have

D - 410 = ma

where D is the driving force of the engine.
Click to expand...

But 2.2ms-1 is the speed, not the acceleration.
 
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