Question

What is the normal force on the object of mass m1 (20 kg) shown in the diagram? What is the acceleration of the object?

Answer 1

WHERE IS THE DIAGRAM MATE ???

Answer 2

(a) The weight of the box depends on the value of g:

FG = m2g = (20.0 kg)(9.80 m/s2

) = 196 N.

We find the normal force from

·Fy

= may

;

FN – m 2g = 0, which gives FN = m2g = 196 N.

(b) We select both blocks as the object and apply Newton’s

second law:

·Fy

= may

;

FN2 – m1g – m2g = 0, which gives

FN2 = (m1

+ m2

)g = (10.0 kg + 20.0 kg)(9.80 m/s2

) = 294 N.

If we select the top block as the object, we have

·Fy

= may

;

FN1 – m1g = 0, which gives

FN1 = m1g = (10.0 kg)(9.80 m/s2) = 98.0 N.