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Newton’s Laws

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Newton’s Laws

4B investigate and describe [applications of] Newton’s laws such as in vehicle restraints, sports activates, geological processes, and satellite orbits;

Law of Inertia

- An object in motion remains in motion or an object at
rest remains at rest unless acted on by an unbalanced force.

- Object is at rest or at constant velocity
- Forces acting on objects are balanced – no net force
- Seatbelts; if no seatbelt car stops and passenger slides forward

With seat belt.

Without seat belt.

- Unbalanced forces (net force) cause an object to
accelerate in the direction of the net force.

- Net force = mass x acceleration
(Newton’s Second Law)

- FNet = m x a
- Units: kg-m/s2 , or Newton (N)

a = 3 m/s2 FNet = m x a

2 kg x 3 m/s2 = 6 N

- For every action there is an equal and opposite reaction
- Forces occur in pairs
- Forces act on two different objects

Action: Rocket pushes gases down.

Reaction: Gases push rocket up.

1. The picture above shows the directions in which water leaves this scallop’s shell. Which picture below shows the direction the scallop will move?

- [Option 1]
- [Option 2]
- [Option 3]
- [Option 4]

2.A wet bar of soap slides 1 meter across a wet tile floor without appearing to slow down. Which of these statements explains why the bar of soap fails to slow down?

- A constant force on an object produces constant positive acceleration.
- An object in motion tends to remain in motion in the absence of an external force.
- A moving object having constant velocity contains kinetic energy.
- An object’s weight is proportional to its mass.

3.A hockey player pushed a puck toward the opposite side of a level ice rink. The player expected the puck to continue all the way across the ice, but the puck slowed and stopped before reaching the other side. Which of these best explains why the puck failed to slide all the way to the opposite side?

- The puck’s temperature changed.
- An upward force acted on the puck.
- The puck’s momentum remained unchanged.
- An opposing force acted on the puck.

4.The frog leaps from its resting position at the lake’s bank onto a lily pad. If the frog has a mass of 0.5 kg and the acceleration of the leap is 3 m/s 2, what is the force the frog exerts on the lake’s bank when leaping?

- 0.2 N
- 0.8 N
- 1.5 N
- 6.0 N

- The ground pushes the rocket up while exhaust gases push down on the ground.
- Exhaust gases push down on air while the air pushes up on the rocket.
- The rocket pushes exhaust gases down while the exhaust gases push the rocket up.
- Gravity pulls the rocket exhaust down while friction pushes up against the atmosphere.

6.After shooting a cannonball, a cannon recoils with a much lower velocity than the cannonball. This is primarily because, compared to the cannonball, the cannon has a —

- much greater mass
- smaller amount of momentum
- greater kinetic energy
- smaller force applied to it

- An increase in the satellite’s forward momentum
- An increase in solar energy striking the satellite
- A decrease in the satellite’s size
- A decrease in the satellite’s velocity

8.When the air is released from a balloon, the air moves in one direction, and the balloon moves in another direction. Which statement does this situation best illustrate?

- What goes up must come down.
- For every action there is an equal and opposite reaction.
- The shape and size of an object affect air resistance.
- The acceleration due to Earth’s gravity is 9.8 m/s2.

- An increase in the length of a day on Earth
- An increase in the distance between Earth and the sun
- An increase in the number of planets orbiting the sun
- An increase in the masses of Earth and the sun

10.An athlete sitting in a wheelchair at rest throws a basketball forward. Since the athlete and the wheelchair have greater mass than the basketball has, the athlete and the wheelchair will —

- move backward at a lower speed than the basketball moves forward
- travel the same distance as the basketball but in the opposite direction
- move backward at a higher speed than the basketball moves forward
- have the same forward momentum as the basketball

- inertia
- Mass
- A reaction force
- A gravitational force

12. The pictures show how an air bag functions in a collision. How much momentum in kg m/s does the air bag absorb from the crash-test dummy if all the crash-test dummy’s momentum is absorbed by the air bag? Record and bubble in your answer to the nearest whole number on the answer document.

630

13.How many newtons of force does a 50.0 kg deer exert on the ground because of gravity? Record and bubble in your answer on the answer document.

490