Unit 4 Activity 2 Extension C Quiz

In a question earlier in this extension, you considered the situation of moving a couch at a constant speed. You concluded that to move the couch at a constant speed, you would need to push it with a force that exactly balances the frictional force of 50 N acting on the couch.Now consider a situation in which the couch is at rest. You push on the couch with a force of 25 N--and the couch still does not move. Which one of the force diagrams below best describes this situation?

C

Several children of different ages and sizes are playing a "tug-of-war" game over a large box of toys. The force diagrams below indicate the forces that between one and four children are exerting on the box at different times. The friction force that the floor exerts on the box is also shown. In each case, the box is moving to the right (as indicated by the red speed arrow).

C

Consider the force diagrams for four low-friction carts shown below. Each cart is subject to pushes from two fans (not shown) mounted on opposite ends of the cart. The forces the fans exert of the carts are shown. All four carts are moving to the right (the speed arrows are not shown). In each case, the cart experiences a small friction force in the opposite direction to its motion. These friction forces are also shown. Each cart has a mass of 1 kg, but three of the carts also carry objects that contribute to their total mass. The total mass of each cart and the object it carries (if any) is indicated in the force diagrams below. Which cart experiences the greatest rate of change in speed?

D