When you climb, earth exerts gravitational force on pack in downward direction(pointing towards the center of earth).
In order to climb, you need to work against work done by gravity on the pack.
Hence work done by you = work done by gravity on pack
= Force x displacement = 70 x 30 = 2100 J.
So you need to do 2100 joules of work to lift your pack.
Power is the rate of work done.
Therefore power = work done by you/time(in seconds)
= 2100/600 =3.5 watts
B. +Q, + W are the correct sign
Answer: 83.8 m/s
Explanation:
momentum of shell = momentum of cannon
M(s) × V(s) = M(c) × V(c)
M(s) = mass of shell, V(s) = velocity of shell
M(c) = mass of cannon, V(c) = velocity of cannon
100kg × 75m/s = 90kg × V(c)
7500 = 90 × V(c)
7500 ÷ 90 = V(c)
83.3 = V(c)