Newton's 1st Law
State Newton’s First Law of Motion in your own words, AND identify what determines how much inertia an object has.
An object at rest stays at rest, and an object in motion stays in motion unless acted upon by an unbalanced force.
Mass determines how much inertia an object has.
Using the formula F = m x a, calculate the net force required to accelerate a 5kg bowling ball at 4m/s2
20N
Explain an example of Newton's Third Law of Motion in your own words
answers vary but should explain something that shows "For every action force, there is an equal and opposite reaction force"
Name two factors that determine how much friction force exists between two solid surfaces sliding past each other.
The types of surface materials and how hard the surfaces are pressed together
A runner travels a distance of 100m in 20s. Calculate their average velocity
5m/s
You are riding in a car moving forward at 45mph when the driver suddenly slams on the brakes. Explain why your body lurches forward using the word inertia.
Your body has inertia and wants to keep moving forward at 45mph. The car stops, but your body keeps moving until the seatbelt applies an outside force to stop you.
A net force of 50N is applied to a 10kg cart. Calculate the acceleration of the cart.
5m/s2
A swimmer pushes backward on the water with a force of 80N. What is the magnitude and direction of the force the water exerts on the swimmer?
80N
You push a heavy wooden box with 40N of force, but it does not move. How much static friction force (in Newtons) holding it in place?
40N
Using the work formula, calculate how much work is done when a weightlifter exerts a force of 300N to lift a barbell 2m high.
600J
A hockey puck is flicked across a sheet of ice and slowly comes to a stop. A student claims this violates Newton's First Law because no force was pushing it. Explain why the student is wrong.
The puck stops because of an outside force acting on it: friction between the puck and the ice.
If you push a shopping cart with same amount of force and suddenly double the mass inside the cart, what happens to the acceleration of the cart?
The acceleration is decreased/cut in half (or divided by 2)
A hammer hits a nail with a force of 200N. Identify the action force and the reaction force.
Action: Hammer exerts 200N on the nail.
Reaction: Nail exerts 200N back on the hammer.
Which type of friction is generally greater for the same two surfaces: Static Friction or Sliding Friction?
Static Friction. (It takes more force to get an object moving than to keep it sliding).
A student pushes hard against a heavy brick wall with a force of 150N for 10s, but the wall does not move at all. How much work was done on the wall?
0J
A box is being pushed across a floor. A forward force of 25N pushes to the right, and a friction force of 25N pushes to the left. Describe the motion of the box using Newton's First Law.
The net force is 0N, so the box is either completely at rest OR moving at a constant velocity in a straight line.
A force of 120N causes a shopping cart to accelerate at a rate of 3m/s2. Calculate the mass of the shopping cart.
40kg
A mosquito crashes into the windshield of a moving bus. Compare the force the bus exerts on the mosquito to the force the mosquito exerts on the bus.
The forces are equal. (By Newton's 3rd Law, action-reaction forces are always equal in magnitude).
Explain why dragging a heavy wooden crate across a concrete driveway requires more force than dragging the same crate across a ice rink.
Concrete has a rougher surface than ice, which creates more microscopic catching between surfaces and results in a higher friction force.
An astronaut weighs 600N on Earth. On the Moon, gravity is only 1.6m/s2. What happens to the astronaut's mass on the Moon, and what happens to their weight?
Their mass stays the same; their weight decreases (becomes smaller).
A textbook sits completely still on a classroom desk. Identify the two forces acting on the book, and state whether they are balanced or unbalanced.
Gravity (weight) pulling down and the Normal Force pushing up.
They are balanced (equal in size, opposite in direction).
An elevator has a total mass of 500kg. Calculate its weight (W)
4,900N
If action and reaction forces are always equal and opposite, explain why a cannon and a cannonball don't move with the same acceleration when fired.
Because they have very different masses (a = F/m). The force is equal, but the cannonball has a tiny mass so it accelerates rapidly, while the heavy cannon barely accelerates back.
Why is it usually harder to get a heavy couch to start sliding across a carpet than it is to keep it sliding once it is already moving?
Static friction (resisting starting motion) is stronger than Sliding friction (resisting sliding motion).
A motor does 1,200J of work in 4s. Calculate the power output of the motor.
300W