Newton's Laws
This law of Newton's best explains the reason for wearing a seatbelt when driving a car.
What is Newton's First Law of Motion?
This is the tension when a rock is suspended from a string and moves downward at constant speed with air resistance ignored.
What is tension is equal to the weight of the rock?
This is the mass of a hockey puck that accelerates at 75 m/s2 when a 30 N force is applied to it.
What is 0.4 kg?
This is the fully labelled free body diagram for a book resting on a table.
Gravity down and Normal Force up
This is the characteristics the coefficient of friction depends on.
What is the roughness of the two surfaces in contact?
This is Newton's First Law and an example of it.
What is an object at rest will remain at rest, and an object in motion will remain in motion at constant velocity unless acted upon by a net external force. Example: A book on a desk stays at rest; a hockey puck slides across ice at constant velocity.
This is the tension when a rock is suspended from a string and accelerates upwards with air resistance ignored.
What is tension is greater than the weight of the rock?
This is the acceleration when a 10 kg object experiences a 15 N force.
What is 1.5 m/s2?
This is the fully labelled free body diagram for a car parked on a frictionless icy hill at angle θ and the direction it will accelerate.
Normal and friction at angles, gravity straight down (or vice versa)
What is down the slope?
The sum of the force statements for a girl sledding through deep snow.
\sumF_x=-F_f=ma
\sumF_y=F_N-F_g=0
This is what happens when an astronaut throws a wrench in space.
What is the astronaut will move away from the wrench with an equal and opposite force?
This is the reason that a scale in an elevator will give a person a reading greater than their weight.
What is the elevator is accelerating upwards and the scale is showing the normal force?
This is the magnitude of the horizontal acceleration of a 4.5 kg block when two forces act on it: one force of 12 N to the right and another force of 6 N to the left.
What is 1.33 m/s/s?
This is both fully labelled free body diagram for a cannonball fired from a frictionless cannon on wheels immediately after firing.
Cannon: Reaction force, normal, gravity
Cannonball: Applied Force, gravity
Reaction and Applied in opposite directions
The sum of the force statements for a car accelerating down a frictionless icy slope during an ice storm at angle θ.
netFx=Fgcos(90-θ)=ma
netFy=Fn-Fgsin(90-θ)=0
This is why a lighter hockey puck accelerates more than a heavier puck when struck with the same force.
What is Newton's Second Law? (When force is constant, mass and acceleration are inversely proportional.)
This is the tension in each rope when a 30 kg sign is hanging at rest from two vertical ropes.
What is approx. 150N in each rope?
This is the force of friction and the acceleration if an applied force of 200 N is applied horizontally to a 50 kg box on a surface with a coefficient of kinetic friction of 0.25.
What is 122.5 N and 1.55 m/s/s?
The fully labeled free diagram for Two trucks towing a semi-truck out of a ditch, the semi-truck is applying a forward driving force, the tensions in the towing chains apply the forces T1 and T2 at angles of 25.0° and 15.0° w, respectively, with respect to the semi-truck’s forward axis. However the ditch is applying a resistive force R.
Applied forward, resistive backwards, tensions at an angle on opposite side of the applied force
The sum of the force statements for a window washer pulling herself up at a constant acceleration.
\sumF=ma=2F_T-F
This is the relative motion of a cannon and cannonball on a frictionless surface after firing.
What is the cannonball exerts an equal and opposite force on the cannon, so the cannonball accelerates forward rapidly while the cannon recoils backward slowly?
This is the force conditions at terminal velocity.
What is air resistance equals weight at terminal velocity?
Will a 60 kg person slip off a raft that is accelerating at 4.5 m/s/s, if the coefficient of friction between their feet and the raft is 0.4. Why?
(I could not word this as a statement)
Yes because their max static friction force is 235.2 N and they are experiencing a net force of only 270N.
This is both fully labelled free body diagrams for a crate of mass M is on a frictionless inclined plane at angle θ, connected by a cord over a pulley to a hanging mass m.
Crate: weight down, tension up slope, friction down slope
Hanging mass: Tension up, gravity down
The sum of the force statements for two masses (m₁ and m₂, where m₁ > m₂) connected by a cord over a frictionless pulley suspended by cord C. After the masses are released.
\sumF_1=-m_1a=F_T-F_(g1)
\sumF_2=m_2a=F_T-F_(g2)