An object at rest stays at rest, and an object in motion continues moving at constant velocity in a straight line, unless acted upon by a net external force.
Things keep doing what they're doing unless something pushes or pulls them.
Showing a random 20 of 50 problems.
Example 1
medium
A 2 kg object hangs at rest from a spring. Spring force is F up, weight 19.6 N down (g=9.8). Find F.Mass hanging at rest from a spring — find spring force F
Example 2
hard
A satellite orbits Earth at constant speed in a circular orbit. Is it in equilibrium according to Newton's first law? Explain.
Example 3
easy
Why do you wear a seatbelt in a car?
Example 4
medium
In an accelerating bus, a hanging strap tilts backward. Why?
Example 5
medium
Two equal teams pull a rope, neither side moving. What is the net force on the flag at the center?
Example 6
easy
A spacecraft drifts in deep space, far from any star. No engine fires. What happens to its velocity?
Example 7
hard
A traffic light hangs at the center of a horizontal cable. The cable sags at angle θ=10° below horizontal on each side. The light's weight is 200 N. Find the tension in each side of the cable.Traffic light on sagging cable — find cable tension T
Example 8
medium
A ball rolls on a perfectly smooth, infinite horizontal surface. After being released with velocity v0, how long does it continue moving?
Example 9
medium
A ball rolls on a level frictionless surface at 3 m/s. Predict its speed after 10 s.
Example 10
medium
An astronaut floating in the ISS pushes off a wall with 50 N for 0.5 s. Her mass is 60 kg. After her hand leaves the wall, describe her motion.
Example 11
medium
A 4 kg sled moves at constant 5 m/s while a rope pulls it with 12 N. Find the friction force.Sled at constant velocity — friction force equals rope tension
Example 12
easy
Tablecloth pulled fast leaves dishes nearly in place. What property explains this?
Example 13
hard
A balloon rises at constant velocity. Its weight is 80 N, buoyant force is B, and air drag is 30 N downward. Find B.Balloon at constant ascent velocity — find buoyant force B
Example 14
easy
A car turns at constant speed around a curve. Is there a net force?
Example 15
challenge
A coin sits on a card over a cup. The card is flicked sideways and the coin drops into the cup. Explain using the first law and identify why the coin barely moves sideways.
Example 16
medium
A bicyclist moves at constant velocity on level ground. The pedaling produces a forward force of 40 N. What is the magnitude of opposing (friction + drag) forces?Bicyclist at constant velocity — opposing force equals pedaling force
Example 17
medium
A hockey puck slides across a frictionless ice surface at 5 m/s. What is the puck's velocity after 10 seconds?
Example 18
easy
A spacecraft drifts in deep space with its engines off. What happens to its velocity?
Example 19
easy
Newton's first law is also called the law of what?
Example 20
challenge
A 2 kg block rests on a wedge of 30°. The wedge sits on a frictionless floor and is given horizontal acceleration a such that the block does not slide relative to the wedge (no friction between block and wedge either). Find a. Use g=9.8 m/s2.