1. Locomotion
Study Guide Review

2. 1. Drag force would affect which of the following?
A. A runner’s shoes on the sidewalk.
B. A fish’s fins in the water.
C. A bird’s wings in the air.
D. B and C.

3. A cat is chasing a mouse in a straight line
A cat is chasing a mouse in a straight line. Suddenly the mouse turns and runs in a different direction. Use the concept of Newton’s Third Law to describe how the cat can change direction to follow the mouse.
A: In order to change direction, the cat must apply a force to the ground. According to Newton’s Third Law, when the cat exerts a force on the ground, the ground will push back with an equal and opposite force. By exerting force on the ground away from the mouse, the ground will push the cat in the direction of the mouse.

4. True or False: Stride length is determined by the number of legs that an animal has.
A: False
Kyle is two meters tall. Liz is one meter tall. When they hike together, Liz often complains that they are walking too fast, but Kyle disagrees; he never feels like they are walking quickly. What might be the cause of their disagreement?
A: As leg length increases, stride length increases. Since Kyle is taller than Liz, he probably has longer legs and a larger stride length than Liz. If this were the case, his legs would cover more distance than Liz. Liz would therefore have to move her legs faster to keep up.

5. True or False: Decreasing the total surface area on a bird’s wings increases the drag force it experiences when falling to the ground.
A: False
A tiger’s paws and a dolphin’s fins are very different in shape. Explain how both creatures use force to move through their environment.
A: Because both animals have different limbs and environments, they must generate different types of force to locomote. The tiger, moving on land, must exert force on the ground with its paws. The Earth will push back and move it forward. The dolphin instead must exert force on the water with its fins. This will cause the water to push back, moving the dolphin forward.

6. When a frog swims through water, it often needs to adjust the drag force it encounters. How can the frog reduce drag force as it swims?
Closing its webbed feet.
Spreading its webbed feet out.
Increasing the speed of its leg movement.
A and C.

7. True or False: If the Earth’s surface didn’t exert force, then no movement on the ground would be possible.
A: True
We can determine the velocity of which of the following?
A car driving 100 km/h.
A bike moving north at 20 m/s.
A fish swimming at 0.1 m/s.
A and C.

8. A dog is running in a straight line down a sidewalk. She wants to stop
A dog is running in a straight line down a sidewalk. She wants to stop. In which direction does the dog need to exert force in order to slow down?
In the direction she’s running.
In the opposite direction that she is running.
To the left side of her body.
None of the above.

9. A fish is swimming through the ocean at 10 cm/s
A fish is swimming through the ocean at 10 cm/s. It suddenly speeds up to 30 cm/s to avoid a predator. After avoiding the predator, it slows down to 5 cm/s. At what point does the fish experience the most drag force?
Swimming 10 cm/s.
Swimming 30 cm/s.
Swimming 5 cm/s.
It experienced equal drag force at every speed.

10. When we walk, our feet apply force to the ground
When we walk, our feet apply force to the ground. How much force does the ground push back with?
The ground pushes back with more force.
The ground pushes back with equal force.
The ground pushes back with less force.
The ground does not push back with any force.

11. Michael’s bike exerted force on the Earth, and is bike moved forward
Michael’s bike exerted force on the Earth, and is bike moved forward. Why did this happen?
A: The Earth has more mass than the bike.
State Newton’s First Law of Motion.
A: An object in a state of uniform motion stays in that state unless acted upon by an outside force.
State Newton’s Third Law of Motion.
A: For every force there is an equal and opposite force.

12. What is an adaptation?
A: Adjustment to environmental conditions; modification of structure of a population of organisms that makes the organisms more fit for existence under the conditions of their environment.
What is surface area? How do you calculate it?
A: The amount of the surface that covers the object in question or that an object covers. It is calculated by multiplying height by width.

13. A push or pull on an object is a __________.
A: Force
How does Newton’s Third Law of Motion apply to the movement of animals on land?
A: In order for a human or animal to walk on land, a force is needed. As a step is taken, a force is exerted on the Earth. The Earth exerts an equal force in return and in the opposite direction of the original force. When the direction of an animal or a person changes or when they slow down or speed up, forces are exerted to which the Earth exerts an equal and opposite force in return. This application of equal an opposite forces, as described in Newton’s third law of motion, gives humans and animals the ability to locomote and, therefore, survive in their environment.

14. How do physical characteristics of a land animal determine its ability to move?
A: As leg length increases, stride length also increases. Therefore, on would assume that stride rate, or the number of strides in a given period of time, is also related to leg length. This relationship may allow greater equivalence between prey and predator. Organisms with shorter limbs must take more strides per unit of time than an organism with longer limbs.

15. What is drag force? How did we demonstrate it in lab?
A: Drag force is the resistance applied to an object by a fluid. Drag force always acts opposite to the direction of relative motion. We demonstrated this in lab when we used the spring scales to pull the ruler across the water.

16. How are forces and motion of organisms in water similar or different to organisms that locomote on land?
A: Organisms on both land and water must adapt to forces present. On land, organisms exert a force on the ground in order to locomote, and the ground exerts an equal force in the opposite direction in response. In water, organisms such as fish and ducks, exert a force on the water in order to locomote and the water exerts an equal force in the opposite direction. When a duck pushes with its webbed feet, the opposite and equal force encountered by the force exerted by the duck is called drag force.

17. Think of the way a fish is shaped, with a small front surface area and a large side surface area. How does the fish’s shape relate to the relationship between the surface area and drag force?
A: The front of a fish has a small surface area, which minimizes the amount of drag force that acts upon it as it moves forward. The fish’s largest surface area is on its sides. This maximizes the amount of drag force that acts upon it as it swims. The fish moves forward because there is a greater amount of drag force acting on the sides than on the front of the fish, and because the force exerted by the fish as it pushes against the water is less than the drag force exerted on its sides. Therefore, the fish’s shape allows it to move easily through the water.

18. How does the adaptation of a duck’s webbed feet affect its movement in the water? Explain your answer in terms of the relationship between drag force and surface area.
A: A duck pushes against the water with its open webbed feet, propelling itself forward, then curls its toes and pulls its feet against its body as it move the feet forward for another stroke. The duck is using drag force to its advantage by pushing against the water with its open webbed feet. Drag force is the force that pushes the duck forward in the water. Therefore, the duck uses the large surface area of its open webbed feet to increase drag force. The duck minimizes drag force when it pulls its folded feet forward beneath its body.

19. How does the effect of drag force on surface area affect flying animals?
A: As surface area increases, drag force increases. Drag force acts in the opposite direction of an object’s fall, thus slowing the object’s descent. Wings increase the surface area of birds. The increases surface area decreases a bird’s chances of falling to the ground. If birds did not have wings, and instead had limbs like animals that live on the ground, their surface area would be greatly reduced, thereby decreasing their drag force when descending.