Answer : The correct option is, (D) A machine does 400 joules of work in 5 seconds.
Explanation :
Power : It is defined a the rate of doing work per unit time.
Formula used :

where,
P = power
w = work done
t = time
Now we have to determine the rate of power for the following options.
(A) A machine does 200 joules of work in 10 seconds.

(B) A machine does 400 joules of work in 10 seconds.

(C) A machine does 200 joules of work in 5 seconds.

(D) A machine does 400 joules of work in 5 seconds.

From this we conclude that, a machine does 400 joules of work in 5 seconds has the highest rate of power.
Hence, the correct option is, (D)
Answer:
20 N in West direction.
Explanation:
opposite forces cancel each other. so 20 N in north and 20N in south cancel each other. In west and east direction...
70N in west-50N in east= 20N in west
Answer:
Magnetism is the force exerted by magnets when they attract or repel each other.
The acceleration formula goes like this: a= (vf-vi)/t so it would be (13-4)/3 Thus the answer is 3m/s^2