20.4 years is 20.4/10.2 = 2 half-life cycles, which means a quarter of the starting mass or 15.2 g will remain after this time.
Answer:
159 N
Explanation:
The force of friction, Fr is a product of coefficient of feiction and the normal force. Therefore, Fr=uN where N is the normal force and u is coefficient of friction. Here, we have two coefficients of friction but since it is sliding, then we use coefficient of kinetic energy. Substituting 0.25 for u and 636 N for N then
Fr=0.25*636=159 N
Therefore, the force of friction is equivalent to 159 N
1200 watt seconds
1.2. Kw seconds
1.2/ 3600 KWh