1.You jump out of an airplane and open your parachute after an extended period of free fall.
Part A.To decelerate your fall, must the force exerted on you by the parachute be greater than, less than, or equal to your weight?
greater than
less than
equal to
Part B.Choose the best explanation from among the following:
Choose the best explanation from among the following:
A parachutes can only exert forces that are less than the weight of the skydiver.
The parachute exerts a force exactly equal to the skydiver’s weight.
To decelerate a skydiver in free fall, the net force acting on the skydiver must be upward.
2.Researchers have found that a gecko’s foot, like the one shown in the figure (Figure 1) , is covered with hundreds of thousands of small hairs (called setae) that allow it to walk up walls and even across ceilings. A single foot, whose toe pads have a total surface area of
1.0cm2, can attach to a wall or ceiling with a force of 11 N.
Part A.How many 250-g geckos could be suspended from the ceiling by a single foot? Express your answer as an integer.
Part B.Estimate the force per square centimeter that your body exerts on the soles of your shoes, and compare with the 11N/cm2 of the sticky gecko foot.
Estimate the force per square centimeter that your body exerts on the soles of your shoes, and compare with the of the sticky gecko foot.
The force per square centimeter exerted on the soles of a 700-N person’s two feet is equal 100 N/cm2. In fact, a human foot could support the weight of three . human-sized geckos.
The force per square centimeter exerted on the soles of a 700-N person’s two feet is equal 10 N/cm2.
The force per square centimeter exerted on the soles of a 700-N person’s two feet is equal 1.8 N/cm2. In fact, a single human-sized gecko foot could support the weight of three humans that each weigh 700 N.
3.A person who normally weighs 700 N is riding in a rather swift elevator that is moving at a constant speed of 9.8 m/s. If this person is standing on a bathroom scale inside the elevator, what would the scale read?
Pick one of the four
more than 700 N700 Nless than 700 NIt could be more or less than 700 N, depending on whether the elevator is going up or down.
4. When a 45-kg person steps on a scale in an elevator, the scale reads a steady 480 N. Which of the following statements must be true? (There could be more than one correct choice.)
Check all that apply.
Check all that apply.
The elevator is accelerating downward at a constant rate.
The elevator is moving downward at a constant rate.
The elevator is accelerating upward at a constant rate.
The elevator is moving upward at a constant rate.
From the given information, we cannot tell if the elevator is moving up or down.
5.A very light ideal spring having a spring constant (force constant) of 8.2 N/cm is used to lift a 2.2-kg tool with an upward acceleration of 3.25 m/s2. If the spring has negligible length when it us not stretched, how long is it while it is pulling the tool upward?
Express your answer using two significant figures.