Net Force Ninjas
A robot is pulled 75 N east and 45 N west. What is its net force?
30 N East
A student slides identical hockey pucks across carpet and polished tile at the same initial speed. On which surface will a puck likely travel farther?
A. Carpet
B. Polished tile
C. Both equally
D. Neither surface
polished tile
A student tests how the weight of a model car affects the distance it travels when released from the same ramp height. What is the independent variable?
A. Distance traveled
B. Ramp height
C. Weight of the car
D. Type of floor
C. Weight of the car
A spacecraft moves at a constant velocity in deep space with no net external force. What will happen?
A. It gradually stops
B. It continues at constant velocity
C. It speeds up continuously
D. It immediately changes direction
B. it continues at constant velocity
An astronaut carries a 4 kg science instrument from Earth to the Moon. What happens to its mass and weight?
A. Both decrease
B. Mass stays the same; weight decreases
C. Mass decreases; weight stays the same
D. Both stay the same
B. Mass stays the same; weight decreases
A drone experiences 90 N upward and 90 N downward. What can you conclude?
The forces are balanced
Which change would most likely increase friction between a shoe and the floor?
A. Adding rubber tread
B. Polishing the floor
C. Adding lubricant
D. Replacing the sole with smooth plastic
Adding rubber tread
Students test how different shoe materials affect friction by measuring the force needed to pull each shoe at constant speed. What is the dependent variable?
A. Shoe material
B. Measured pulling force
C. Distance of the test track
D. The spring scale
B. measured pulling force
A rolling ball gradually slows on a gym floor. What best explains the change in its motion?
A. Motion naturally disappears
B. Its mass is decreasing
C. Friction produces a force opposing its motion
D. Gravity has stopped acting
C. friction produces a force opposing its motion
A swimmer pushes backward on the pool wall with 65 N. What force does the wall exert on the swimmer?
A. 0 N
B. 32.5 N forward
C. 65 N forward
D. 130 N forward
C. 65 N forward
A sled experiences 55 N right, 25 N left, 15 N right, and 10 N left. Calculate the net force.
35 N right
A student pulls the same block at constant speed across two surfaces. Surface X requires 6 N, while Surface Y requires 13 N. Which conclusion is supported?
A. X has more friction
B. Y has more friction
C. Both have equal friction
D. The block is heavier on Y
Y has more friction
A team investigates how added mass changes a cart's acceleration. Which factor should remain constant?
A. Added mass
B. Acceleration
C. Applied pushing force
D. The results
C. applied pushing force
A 40 N force acts on two carts, one with a mass of 2 kg and another with a mass of 8 kg. Which cart has greater acceleration?
A. 2 kg cart
B. 8 kg cart
C. Both accelerate equally
D. Neither accelerates
A. 2kg cart
A scientist compares two explanations for why a rolling object stops. Which evidence is more scientifically persuasive?
A. A popular opinion
B. A claim from a famous scientist
C. A single guess
D. Repeatable, controlled experimental results
D. Repeatable, controlled experimental results
A platform has 220 N upward and 340 N downward forces, plus equal opposing horizontal forces. What is its acceleration direction?
Downward
An engineer wants a moving cart to lose less energy to friction. Which modification is most appropriate?
A. Increase surface roughness
B. Add more mass
C. Oil moving parts
D. Press the wheels harder against the track
Two groups test different ramp surfaces, but one group also changes the ramp angle. Why is comparing their results problematic?
A. They measured too much data
B. The independent variable is missing
C. They changed more than one relevant variable
D. The ramps must be identical color
C. they changed more than one relevant variable
A team pulls a rope 180 N to the left. Ignoring other horizontal forces, how hard must the opposing team pull to produce acceleration to the right?
A. Exactly 180 N
B. Any force below 180 N
C. More than 180 N
D. 0 N
C. more than 180 N
A box rests on a level shelf. Which statement correctly describes the gravitational and support forces acting on it?
A. Gravity is the only force
B. The shelf pushes downward
C. Gravity and the upward support force are equal
D. The upward force must exceed gravity
C. Gravity and the upward support force are equal
Three students push a supply cart. Student A pushes with 120 N to the right, Student B pushes with 75 N to the right, and Student C pushes with 140 N to the left. Friction exerts another 25 N to the left. What is the net force and in which direction will the cart accelerate?
30 N right
Two identical toy cars are released from the same height on identical ramps. One ramp is covered with felt, while the other is covered with smooth plastic. The car on the plastic ramp reaches the bottom faster. Which explanation best supports these results?
A. The plastic increases the gravitational force acting on the car.
B. The felt produces greater friction, opposing the car's motion.
C. The plastic decreases the mass of the car.D. The felt creates a greater downward gravitational force.
D. The felt creates a greater downward gravitational force .
B. The felt produces greater friction, opposing the car's motion.
Students investigate whether the mass of a toy truck affects its acceleration. They add different masses to the truck, push it with the same force each time, and measure its acceleration. Which answer correctly identifies the independent, dependent, and controlled variables?
A. Independent: force; dependent: mass; controlled: acceleration
B. Independent: acceleration; dependent: force; controlled: mass
C. Independent: mass; dependent: acceleration; controlled: applied force
D. Independent: mass; dependent: applied force; controlled: acceleration
C. Independent: mass; dependent: acceleration; controlled: applied force
A spacecraft travels through space at a constant velocity. Its engines suddenly produce a force opposite its direction of travel. Assuming no other forces act on it, what happens?
A. It immediately stops because forces always stop motion.
B. It continues at the same velocity because it is already moving.
C. It immediately travels in the opposite direction.
D. It initially slows down because the net force causes acceleration opposite its motion
D. It initially slows down because the net force causes acceleration opposite its motion
A scientist measures a 12 kg object on Earth and then takes it to the Moon. The object's weight is approximately one-sixth of its Earth weight. Which statement correctly explains this observation?
A. The object loses five-sixths of its matter on the Moon.
B. Its mass stays 12 kg, but its weight decreases because the Moon's gravitational field is weaker.
C. Its mass and weight both decrease by the same amount.
D. The object has no mass because gravity is weaker on the Moon
B. Its mass stays 12 kg, but its weight decreases because the Moon's gravitational field is weaker.