Inertia & Equilibrium
A hockey puck slides across a frictionless floor at 10 m/s. How much horizontal net force is needed to keep it moving at this speed?
0 N
(Inertia keeps it moving at constant velocity without net force).
Which control in a car can change the vehicle's velocity vector without changing its speed?
The steering wheel.
A rock is dropped off a cliff from rest. What is its downward speed after falling for 3 seconds?
30 m/s
A baseball is thrown straight up into the air. At the exact peak of its trajectory, what is its acceleration?
10 m/s/s downward
Car A driving at 60 km/h is rear-ended by Car B traveling in the same direction at 68 km/h. What is the relative speed of the collision?
8 km/h
You push horizontally on a heavy cabinet with 50 N of force, but it does not move. What is the magnitude of the static friction force?
50 N
(Static friction matches the applied force until motion starts).
True or False: A race car traveling around a circular track at a steady 50 mph is NOT accelerating.
False (Direction is constantly changing, which means velocity is changing and the car is accelerating).
How far does a dropped marble fall during its first 2 seconds of free fall?
20 m
If a ball is launched straight up at 30 m/s, how many seconds does it take to reach peak height?
3 s
An airplane flies north at 150 km/h airspeed while encountering a 30 km/h headwind blowing directly south. What is its ground speed?
120 km/h
A 100 N framed painting hangs at rest in static equilibrium suspended symmetrically by two vertical wires. What is the tension in each wire?
50 N in each wire.
Name all three vehicle controls in a standard car that can cause an acceleration.
Gas pedal, brake pedal, and steering wheel.
An object is dropped from rest and takes 4 seconds to hit the ground. How high was the drop height?
80 m
If a vertically tossed ball takes 4 seconds to reach its maximum height, what is its total round-trip flight time back to the ground?
8 seconds
A swimmer paddles north across a river at 4 m/s while the river current flows east at 3 m/s. What is the swimmer's speed relative to the shore?
5 m/s
When a stationary bus suddenly accelerates forward, passengers feel pushed back into their seats. What physical property explains this?
Inertia (their bodies tend to stay at rest while the bus moves forward under them).
What is the primary difference between speed and velocity?
Speed is a scalar (magnitude only), while velocity is a vector (magnitude and direction).
You toss a coin straight up while riding inside a train moving smoothly at a constant 100 km/h. Where does the coin land relative to your hand?
Directly back in your hand (it retains the horizontal speed of the train).
A ball is thrown straight up with an initial speed of 25 m/s. Neglecting air resistance, at what speed will it return to your hand?
25 m/s
To cross a flowing river directly without drifting downstream, a boat driver aims angled upstream. How does their shore speed compare to their paddling speed in still water?
Shore speed is less (paddling speed becomes the hypotenuse of the velocity right triangle).
A crate slides across a floor at a constant speed of 2 m/s under a continuous horizontal push of 150 N. What is the net horizontal force on the crate?
0 N (The object is in dynamic equilibrium, so push force equals friction force)
Give an example of a situation where an object's instantaneous speed is zero, but its acceleration is non-zero.
A ball at the exact peak of a vertical throw.
A stone is dropped down a 125-meter-deep canyon. How many seconds does it take to reach the bottom?
5 s
A rocket is launched vertically upward at 40 m/s. What maximum height does it achieve?
80 m
A kayaker paddles upstream at 10 km/h relative to the water against a 10 km/h river current. What is their speed relative to the riverbank?
0 km/h