AP Physics 1 practice problems: cram pack

Formula sheets, the key method steps for every topic and 14 practice problems, with full solutions at the back.

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1Formulas and methods

Kinematics

Velocity
v = v0 + a·t
Displacement
s = v0·t + ½·a·t²
Without time
v² = v0² + 2·a·s
Units
1 m/s = 3.6 km/h

Method

  1. List what you know: v₀, v, a, t and s, with units.
  2. Pick the equation that contains your three knowns and the unknown.
  3. Choose one positive direction and give opposing quantities a minus sign.
  4. Solve and check that the answer is physically sensible.

Newton’s laws

Second law
ΣF = m·a
Weight
W = m·g
Kinetic friction
Ff = μ·N
On a slope
along: m·g·sin θ, normal: m·g·cos θ

Method

  1. Draw a free-body diagram with every force on the body.
  2. Choose a positive direction along the motion.
  3. Split forces into components along and perpendicular to the motion (on a slope: m·g·sin θ along, m·g·cos θ into the slope).
  4. Apply ΣF = m·a along the motion; friction is μ·N against the motion.

Projectile motion

Components
vx = v0cos θ, vy = v0sin θ
Position
x = vxt, y = h + vyt − ½gt²
Maximum height
H = h + vy²/(2g)
Range (level ground)
R = v0²·sin 2θ/g

Method

  1. Split the launch velocity into components: vx = v₀·cos θ and vy = v₀·sin θ.
  2. The horizontal motion has constant speed; the vertical motion has acceleration −g.
  3. Find the time of flight from the vertical motion.
  4. Use that time in the horizontal motion to find the range.

Circular motion

Centripetal acceleration
a = v²/r = ω²·r
Centripetal force
F = m·v²/r
Angular speed
ω = v/r = 2π/T
Flat curve, friction
vmax = √(μ·g·r)

Work & energy

Kinetic energy
Ek = ½mv²
Potential energy
Ep = mgh
Energy balance
Ek1 + Ep1 + W = Ek2 + Ep2 + losses
Work of friction
W = μ·N·d
Power
P = W/t

Momentum & collisions

Momentum
p = m·v
Conservation
Σm·v (before) = Σm·v (after)
Perfectly inelastic
v′ = (m1v1 + m2v2)/(m1 + m2)
Impulse
J = F·Δt = m·Δv

Method

  1. Choose a positive direction and give each velocity its sign.
  2. Write the total momentum before: Σm·v.
  3. For a perfectly inelastic collision the bodies move together after; for an elastic one kinetic energy is also conserved.
  4. Set momentum before equal to momentum after and solve.

Springs & pendulums

Mass on a spring
T = 2π·√(m/k)
Pendulum
T = 2π·√(L/g)
Angular frequency
ω = √(k/m) = 2π/T
Maximum speed and acceleration
vmax = A·ω, amax = A·ω²
Energy
E = ½·k·A²

2Practice problems

1.KinematicsMedium
t (s)v (m/s)1.875 s15

A car driving at 54 km/h brakes with a constant deceleration of 8 m/s² until it stops. Find the braking distance s.

v₀ = 54 km/ha = −8 m/s²v = 0
s = m
2.KinematicsHard
v₀ = 19 m/s40 m

A ball is thrown straight up at 19 m/s from the edge of a roof 40 m above the ground. Ignore air resistance and use g = 9.81 m/s². Find the greatest height hmax above the ground.

v₀ = 19 m/sh₀ = 40 mg = 9.81 m/s²
hmax = m
3.Newton’s lawsMedium
6 kg2 kg

Masses of 6 kg and 2 kg hang on either side of a light, frictionless pulley, connected by a light string. The system is released from rest. Use g = 9.81 m/s². Find the tension T in the string.

m1 = 6 kgm2 = 2 kgg = 9.81 m/s²
T = N
4.Newton’s lawsHard
m1​ = 9.5 kg8.5 kgθ = 35°

A 9.5 kg block on a ramp at 35° is connected by a light string over a frictionless pulley at the top of the ramp to a hanging 8.5 kg mass. The hanging mass moves down. The ramp is frictionless. Use g = 9.81 m/s². Find the acceleration a of the system.

m1 = 9.5 kgm2 = 8.5 kgθ = 35°μ = 0g = 9.81 m/s²
a = m/s²
5.Projectile motionMedium
48 my = ?v0​ = 26 m/s40°

A ball is kicked from level ground at 26 m/s and 40° above the horizontal towards a wall 48 m away. Ignore air resistance and use g = 9.81 m/s². At what height y does the ball pass the wall?

v₀ = 26 m/sθ = 40°x = 48 mg = 9.81 m/s²
y = m
6.Projectile motionHard
h = 15 mv0​ = 25 m/s15°v = ?

A ball is launched at 25 m/s and 15° above the horizontal from the top of a 15 m cliff. Ignore air resistance and use g = 9.81 m/s². Find the speed v with which it hits the ground.

v₀ = 25 m/sθ = 15°h = 15 mg = 9.81 m/s²
v = m/s
7.Circular motionMedium
r = 2.5 mω = ?

In a fairground rotor, riders stand against the wall of a vertical cylinder of radius 2.5 m. When it spins fast enough the floor drops away and friction holds them up. The coefficient of static friction is 0.5. Use g = 9.81 m/s². Find the smallest angular speed ω in rad/s.

r = 2.5 mμs = 0.5g = 9.81 m/s²
ω = rad/s
8.Circular motionHard
θ = 18°to centrevmax​ = ?

A curve of radius 260 m is banked at 18°, and the coefficient of static friction between tyres and road is 0.2. Use g = 9.81 m/s². Find the highest speed vmax at which a car can take the curve without sliding up and out.

r = 260 mθ = 18°μs = 0.2g = 9.81 m/s²
vmax = m/s
9.Work & energyMedium
40°d = 4 mμ = 0.3

A 10 kg block slides 4 m down a slope at 40° to the horizontal, with a coefficient of kinetic friction of 0.3. Find the work Wf done against friction.

m = 10 kgθ = 40°μ = 0.3d = 4 mg = 9.81 m/s²
Wf = J
10.Work & energyHard
3 kg5 kgμ = 0.25d = 1.5 m

A 3 kg block rests on a rough horizontal table (μ = 0.25). A light string runs from it over a smooth pulley at the edge of the table to a hanging 5 kg block. The system is released from rest. Find the speed v of the blocks after the hanging block has dropped 1.5 m.

m1 = 3 kgm2 = 5 kgμ = 0.25d = 1.5 mg = 9.81 m/s²
v = m/s
11.Momentum & collisionsMedium
800 kg10 m/s2000 kg

An 800 kg car moving at 10 m/s runs into a stationary 2000 kg car and the two lock together. How much kinetic energy ΔK is lost in the collision?

m1 = 800 kgv1 = 10 m/sm2 = 2000 kgv2 = 0
ΔK = J
12.Momentum & collisionsHard
13 m/s14 m/s

A 0.45 kg ball hits a wall at 13 m/s and bounces straight back at 14 m/s. The contact lasts 25 ms. Find the magnitude of the impulse J the wall gives the ball.

m = 0.45 kgvin = 13 m/svout = 14 m/sΔt = 25 ms
J = N·s
13.Springs & pendulumsMedium
t (s)x (cm)1.25 s

A 1.9 kg mass on a spring with k = 390 N/m is pulled 3 cm in the positive direction and released from rest at t = 0. Find its displacement x from equilibrium at t = 1.25 s (with sign).

m = 1.9 kgk = 390 N/mA = 3 cmt = 1.25 s
x = cm
14.Springs & pendulumsHard
3.5 kgk = 430 N/mA = 8 cm

A 3.5 kg mass on a spring with k = 430 N/m is pulled 8 cm from equilibrium and released. Find its maximum acceleration amax.

m = 3.5 kgk = 430 N/mA = 8 cm
amax = m/s²

3Solutions

1.Kinematics

Answer: s = 14.06 m

Motion with constant acceleration: v = v₀ + a·t, s = v₀·t + ½·a·t² and v² = v₀² + 2·a·s. Pick the equation that contains the three things you know and the one you want, and keep the signs consistent with one positive direction.

Units

v₀ = 54/3.6 = 15 m/s

Braking distance

0 = v₀² − 2·a·s → s = v₀²/(2a) = 15²/(2·8) = 14.06 m

Answer

s = 14.06 m
2.Kinematics

Answer: hmax = 58.4 m

Motion with constant acceleration: v = v₀ + a·t, s = v₀·t + ½·a·t² and v² = v₀² + 2·a·s. Pick the equation that contains the three things you know and the one you want, and keep the signs consistent with one positive direction.

Rise above the roof

0 = v₀² − 2·g·Δh → Δh = 19²/(2·9.81) = 18.4 m

Height above the ground

hmax = 40 + 18.4 = 58.4 m

Answer

hmax = 58.4 m
3.Newton’s laws

Answer: T = 29.43 N

Newton’s second law: the net force on a body equals its mass times its acceleration, ΣF = m·a. Draw a free-body diagram, choose a positive direction along the motion, and add every force in that direction: applied forces, friction μ·N against the motion, and the components of gravity.

Acceleration

The net driving force is the difference of the weights; it moves the total mass.

a = (6 − 2)·9.81/(6 + 2) = 4.905 m/s²

Tension from the lighter mass

T − m2·g = m2·a → T = 2·(9.81 + 4.905) = 29.43 N

Answer

T = 29.43 N
4.Newton’s laws

Answer: a = 1.663 m/s²

Newton’s second law: the net force on a body equals its mass times its acceleration, ΣF = m·a. Draw a free-body diagram, choose a positive direction along the motion, and add every force in that direction: applied forces, friction μ·N against the motion, and the components of gravity.

Forces along the string

m₂·g = 83.39 N
m₁·g·sin θ = 53.45 N
μ·m₁·g·cos θ = 0 N

Acceleration of the system

a = (83.39 − 53.45 − 0)/18 = 1.663 m/s²

Answer

a = 1.663 m/s²
5.Projectile motion

Answer: y = 11.79 m

Projectile motion: with no air resistance, x = vxt and y = h + vyt − ½gt². The two directions are independent except that they share the same time.

Time to the wall

vx = 26·cos 40° = 19.92 m/s
t = x/vx = 48/19.92 = 2.41 s

Height at that time

y = 16.71·2.41 − ½·9.81·2.41² = 11.79 m

Answer

y = 11.79 m

The ball is already on its way down at the wall.

6.Projectile motion

Answer: v = 30.32 m/s

Projectile motion: with no air resistance, x = vxt and y = h + vyt − ½gt². The two directions are independent except that they share the same time.

Split the launch velocity

vx = 25·cos 15° = 24.15 m/s
vy0 = 25·sin 15° = 6.47 m/s

Vertical speed at impact

Energy or v² = v₀² + 2as in the vertical direction.

vy = √(6.47² + 2·9.81·15) = 18.33 m/s

Impact speed

v = √(24.15² + 18.33²) = 30.32 m/s

Answer

v = 30.32 m/s

Check with energy: v² = v₀² + 2gh.

7.Circular motion

Answer: ω = 2.801 rad/s

Uniform circular motion: an object moving at speed v on a circle of radius r accelerates towards the centre with a = v²/r, so it needs a net inward force F = m·v²/r. That force is supplied by something real: friction, tension, gravity or a normal force.

Forces on a rider

N = m·ω²·r
μ·N = m·g → μ·ω²·r = g

Angular speed

ω = √(g/(μ·r)) = √(9.81/(0.5·2.5)) = 2.801 rad/s

Answer

ω = 2.801 rad/s
8.Circular motion

Answer: vmax = 37.84 m/s

Uniform circular motion: an object moving at speed v on a circle of radius r accelerates towards the centre with a = v²/r, so it needs a net inward force F = m·v²/r. That force is supplied by something real: friction, tension, gravity or a normal force.

Force balances

Friction points down the slope.

N·(sin θ + μ·cos θ) = m·v²/r
N·(cos θ − μ·sin θ) = m·g

Speed

v = √(260·9.81·0.4992/0.8893) = 37.84 m/s

Answer

vmax = 37.84 m/s
(136.2 km/h)
9.Work & energy

Answer: Wf = 90.18 J

Work–energy principle: the change in kinetic energy equals the work done by all forces. Writing gravity and springs as potential energy (mgh and ½kx²) turns this into a balance: initial energy = final energy + energy lost to friction (μN·d).

Friction force

N = mg·cos θ = 98.1·0.766 = 75.15 N
F = μN = 0.3·75.15 = 22.54 N

Work against friction

Wf = F·d = 22.54·4 = 90.18 J

Answer

Wf = 90.18 J
10.Work & energy

Answer: v = 3.954 m/s

Work–energy principle: the change in kinetic energy equals the work done by all forces. Writing gravity and springs as potential energy (mgh and ½kx²) turns this into a balance: initial energy = final energy + energy lost to friction (μN·d).

Energy released and lost

m₂g·d = 49.05·1.5 = 73.58 J
μ·m₁g·d = 0.25·29.43·1.5 = 11.04 J

Kinetic energy of both blocks

½(m₁ + m₂)v² = 62.54 → v = √(2·62.54/8) = 3.954 m/s

Answer

v = 3.954 m/s
11.Momentum & collisions

Answer: ΔK = 28571 J

Conservation of momentum: when no external force acts during a collision, the total momentum Σm·v before equals the total after. Velocities have a direction, so pick a positive direction and give velocities the other way a minus sign. In an elastic collision kinetic energy is conserved too; in a perfectly inelastic one the bodies stick together.

Common velocity

v′ = m1·v1/(m1 + m2) = 800·10/2800 = 2.857 m/s

Kinetic energy before and after

Kbefore = ½·800·10² = 40000 J
Kafter = ½·2800·2.857² = 11429 J

Energy lost

ΔK = 40000 − 11429 = 28571 J

Answer

ΔK = 28571 J

The lost energy goes into deformation, heat and sound.

12.Momentum & collisions

Answer: J = 12.15 N·s

Conservation of momentum: when no external force acts during a collision, the total momentum Σm·v before equals the total after. Velocities have a direction, so pick a positive direction and give velocities the other way a minus sign. In an elastic collision kinetic energy is conserved too; in a perfectly inelastic one the bodies stick together.

Change in momentum

J = m·Δv = 0.45·(14 + 13) = 12.15 N·s

Answer

J = 12.15 N·s
13.Springs & pendulums

Answer: x = 1.767 cm

Simple harmonic motion: a mass m on a spring of stiffness k oscillates with angular frequency ω = √(k/m) and period T = 2π/ω = 2π·√(m/k). A simple pendulum of length L has T = 2π·√(L/g). With amplitude A, the largest speed is A·ω, the largest acceleration A·ω² and the energy ½·k·A².

Angular frequency

ω = √(390/1.9) = 14.33 rad/s
ω·t = 14.33·1.25 = 17.91 rad

Displacement

x = A·cos(ω·t) = 3·cos(17.91) = 1.767 cm

Answer

x = 1.767 cm
14.Springs & pendulums

Answer: amax = 9.829 m/s²

Simple harmonic motion: a mass m on a spring of stiffness k oscillates with angular frequency ω = √(k/m) and period T = 2π/ω = 2π·√(m/k). A simple pendulum of length L has T = 2π·√(L/g). With amplitude A, the largest speed is A·ω, the largest acceleration A·ω² and the energy ½·k·A².

Angular frequency

ω = √(430/3.5) = 11.08 rad/s

Maximum acceleration

amax = A·ω² = 0.08·11.08² = 9.829 m/s²

Answer

amax = 9.829 m/s²

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