Geologists use the Mohs Harness Scale (aka the Scratch Test) to determine the hardness of a mineral.
For more info, check out http://geology.com/minerals/mohs-hardness-scale.shtml
Answer:
No, it cannot. The car needs the friction of the surface to drive because the car pushes the surface backwards, and the surfaces makes a reaction force pushing the car forward, and that works because of the friction. In a frictionless surface the tires would rotate in the same place
Answer:
<em>The coefficient of static friction between the crate and the floor is 0.41</em>
Explanation:
<u>Friction Force</u>
When an object is moving and encounters friction in the air or rough surfaces, it loses acceleration and velocity because the friction force opposes motion.
The friction force when an object is moving on a horizontal surface is calculated by:
[1]
Where
is the coefficient of static or kinetics friction and N is the normal force.
If no forces other then the weight and the normal are acting upon the y-direction, then the weight and the normal are equal in magnitude:
N = W = m.g
The crate of m=20 Kg has a weight of:
W = 20*9.8
W = 196 N
The normal force is also N=196 N
We can find the coefficient of static friction by solving [1] for
:

The friction force is equal to the minimum force required to start moving the object on the floor, thus Fr=80 N and:


The coefficient of static friction between the crate and the floor is 0.41
Answer:
The value of tension on the cable T = 1065.6 N
Explanation:
Mass = 888 kg
Initial velocity ( u )= 0.8 
Final velocity ( V ) = 0
Distance traveled before come to rest = 0.2667 m
Now use third law of motion
=
- 2 a s
Put all the values in above formula we get,
⇒ 0 =
- 2 × a ×0.2667
⇒ a = 1.2 
This is the deceleration of the box.
Tension in the cable is given by T = F = m × a
Put all the values in above formula we get,
T = 888 × 1.2
T = 1065.6 N
This is the value of tension on the cable.