A block kept on a frictionless horizontal surface is acted upon by a force of 100N, as shown in the figure below. What magnitude of force must be applied on the block from the opposite direction to stop its motion?

A) 50 N
B) 75 N
C) 100 N
D) 200 N​

Can anybody me with this? ? (picture included.)

Two pans of a balance are 24.1 cm apart. the fulcrum of the balance has been shifted 1.33 cm away from the center by a dishonest shopkeeper. by what percentage is the true weight of the goods being marked up by the shopkeeper? assume the balance has negligible mass. answer in units of %.

Agroup of monkeys is trying to cross the river in a rowboat. the maximum buoyant force on the rowboat is 2,000 n. the weight of the rowboat is 1,000 n. each monkey has a weight of 150 n. how many monkeys can safely cross in the rowboat at one time? explain your reasoning, including any calculations you used to find the answer.