Author Question: You push horizontally on a 120-N box that is initially resting on a horizontal table. The ... (Read 99 times)

faduma · **on:** Jul 29, 2018

You push horizontally on a 120-N box that is initially resting on a horizontal table. The coefficient of static friction between the box and the table is 0.75, and the coefficient of kinetic friction is 0.40.

Find the friction force on the box if the push is equal to (a) 84 N; (b) 94 N.

Question 2

Today, the uranium found on Earth contains 0.720 235U (with a half-life of 0.700 billion years) and 99.28 238U (with a half-life of 4.50 billion years).

At a time 2.20 billion years ago, what percent of the uranium on Earth was 238U (assuming that no other uranium isotopes were present)?
A) 95.6
B) 2.18
C) 6.29
D) 8.68
E) 4.53