Answer: question D is trough
Explanation: I learned this already
D. The block should move to the left.
Since the forces are in opposite directions the difference of these forces determines the magnitude and direction of the block. Therefore,
20 N left - 10 N right = 10 N left
Answer:
f' = 2 f
Explanation:
The frequency of the pendulum that swings in simple harmonic motion is given by :

Where
l is the length of pendulum
g is the acceleration due to gravity
If the length of the thread is increased by a factor of 4, such that, l' = 4 l, let f' is the new frequency such that,



f' = 2 f
So, the new frequency of the pendulum will become 2 time of initial frequency. Hence, the correct option is (b) "2f"
Muscles function only by contracting. This makes it necessary for one end of the muscle to be fixed and the other mobile.
Take the bicep for example.
Its origin is at the shoulder and its two heads connect to the bones of the forearm, the radius and ulna.
Now, had the muscle not been fixed at one end, and contracted, it would pull both our shoulder and forearm together resulting in an ineffective movement. The desired motion is to lift the forearm (proximal and distal movement) which can only be achieved if the bicep is fixed at the shoulder and allowed to move at the forearm.
Work done = force x distance
Work done = 50 x 2
Work done = 100J