4.7 Further applications of newton's laws of motion  (Page 6/7)

The figure shows the forces exerted on a block that is sliding on a horizontal surface: the gravitational force of 40 N, the 40 N normal force exerted by the surface, and a frictional force exerted to the left. The coefficient of friction between the block and the surface is 0.20. The acceleration of the block is most nearly

1. 1.0 m/s ² to the right
2. 1.0 m/s ² to the left
3. 2.0 m/s ² to the right
4. 2.0 m/s ² to the left

To simulate the apparent weightlessness of space orbit, astronauts are trained in the hold of a cargo aircraft that is accelerating downward at $g$ . Why will they appear to be weightless, as measured by standing on a bathroom scale, in this accelerated frame of reference? Is there any difference between their apparent weightlessness in orbit and in the aircraft?

A cartoon shows the toupee coming off the head of an elevator passenger when the elevator rapidly stops during an upward ride. Can this really happen without the person being tied to the floor of the elevator? Explain your answer.

A flea jumps by exerting a force of $1\text{.}\text{20}\times {\text{10}}^{-5}\text{N}$ straight down on the ground. A breeze blowing on the flea parallel to the ground exerts a force of $0\text{.}\text{500}\times {\text{10}}^{-6}\text{N}$ on the flea. Find the direction and magnitude of the acceleration of the flea if its mass is $6\text{.}\text{00}\times {\text{10}}^{-7}\text{kg}$ . Do not neglect the gravitational force.

Two muscles in the back of the leg pull upward on the Achilles tendon, as shown in [link] . (These muscles are called the medial and lateral heads of the gastrocnemius muscle.) Find the magnitude and direction of the total force on the Achilles tendon. What type of movement could be caused by this force?

A 76.0-kg person is being pulled away from a burning building as shown in [link] . Calculate the tension in the two ropes if the person is momentarily motionless. Include a free-body diagram in your solution.