Does Static Friction Depend on Mass?

• Jagadish Babu S
In summary: Also, the truck will be pushed sideways by the car as it slides, increasing the effective lateral force. So, in reality, the truck and the car will start to slide at a different angle, but it's still proportional because the forces are all related to the normal force.
Jagadish Babu S
Walter Lewin in his lecture says, a truck and a car on a road will start to slide at a same angle if their tyres are made out of identical material. I know that max. frictional force is proportional to normal force. and if normal force is dependent on mass. shouldn't the frictional force depend on mass?

Jagadish Babu S said:
if normal force is dependent on mass. shouldn't the frictional force depend on mass?
It does. So the frictional force is $R=k\cdot m\cdot g\cdot \cos(\alpha)$ and the force needed to accelerate the car/truck is...

So, you are saying we need more force to move truck(high mass) than a car(low mass) and hence they don't start sliding at same angle on an inclined plane?

Professor Lewin is, unsurprisingly, correct. So why are they the same?
Just look at a block on an inclined plane and work out what has to happen for it to start sliding. What makes it move at all? Is that friction?

I am assuming the more massive object needs more frictional force(k.M.g.sin α) to overcome and also it has large component of force(M.g.cos α) downhill. Object with low mass needs less Frictional force to overcome and has lower component downhill. Both the cases it is the proportionate value that decides when the bodies needs to slide and it happens at same angle independent of mass

On a flat road with identical tires the object with more mass (and therefore more weight) will be harder to slide. The maximum static friction value is a product of the coefficient of friction and the normal force (weight). The greater the weight (all other things being equal) the greater the maximum static friction. This can easily be proven with a flat board, a fishing scale, and some bricks.

On an inclined plane the weight of the truck and the weight of the car contribute to force along the incline, so it's a different situation. The different weights contribute forces along the inclined plane proportional to their contribution to the normal force.

But that's theory. In reality there are other things happening that would keep the truck sliding when the car did slide. For example, the heavier truck will squish the tires deeper into the surface of the road increasing their effective coefficient of static friction. Surface effects are why dragsters can accelerate at rates well above G.

1. Does friction depend on mass?

Yes, friction does depend on mass. Friction is the force that resists the motion of two surfaces rubbing against each other. The amount of friction depends on the weight or mass of the object and the type of surface it is in contact with.

2. How does mass affect friction?

The greater the mass of an object, the greater the amount of force needed to overcome the friction between the surfaces. This is because a heavier object has more contact points with the surface, resulting in a larger frictional force.

3. Is friction affected by the mass of both objects?

Yes, friction is affected by the masses of both objects. The frictional force between two objects is proportional to the weight or mass of both objects. So, if the masses of both objects increase, the frictional force will also increase.

4. Does friction increase as mass increases?

Yes, friction increases as mass increases. This is because the weight or mass of an object determines the amount of contact between two surfaces, which in turn affects the amount of friction between them. As the mass increases, so does the frictional force.

5. How does friction change with mass?

The relationship between friction and mass is directly proportional, meaning as one increases, the other increases as well. This is because as the mass of an object increases, the amount of force needed to overcome the friction between surfaces also increases.

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