A 3 N weight slides down a ramp made of sandpaper. The coefficient of friction is 0.8, and the ramp is at an angle of 50° to the horizontal. How could you calculate the magnitude of the friction force?

A. 3 N × sin(50°)
B. 3 N × 0.8 × 50°
C. 3 N × 0.8 × sin(50°)
D. 3 N × 0.8 × cos(50°)

To calculate the magnitude of the friction force, you can use the equation for the frictional force:

Friction force = coefficient of friction × normal force

The normal force is the force exerted by the surface perpendicular to it. In this case, it is equal to the weight of the object, which is 3 N.

Now, you need to find the coefficient of friction. It is given as 0.8.

Therefore, the magnitude of the friction force can be calculated as:

Friction force = 0.8 × 3 N

So, the answer would be 3 N × 0.8, which is equal to 2.4 N.

The correct option is:

D. 3 N × 0.8