Quick answer: Newton's second law states that the resultant force equals mass times acceleration, ΣF = ma. This Physics 11-12 worksheet on friction and inclined planes gives 20 problems from easy to hard: static and kinetic, net force and acceleration and weight and reaction. The worked answers are on a separate page, and the worksheet is a free printable PDF.
These problems train you to draw free-body diagrams, apply F = ma with friction, resolve weight on a slope and handle connected bodies and lifts. They move from simple resultant forces to tension, friction coefficients from data and towing problems.
They are written for A Level, IB Physics and CBSE Class 11-12 students. Work from level 1 to level 3, sketch the forces each time and use g = 9.81 N/kg.
Level: Physics grades 11-12 (A Level · IB · Class 11-12) · Curriculum: IB A.2
Problem 1 Static and kinetic ★★★
Compare the two main kinds of friction.1. State which one acts when a heavy cupboard is pushed but does not move.
2. Then state which of the two is usually larger at its maximum, and give the symbol for the coefficient of each.
Problem 2 Net force and acceleration ★★★
A car of mass 1200 kg has a resultant forward force of 3000 N.1. Calculate its acceleration.
2. Then calculate the resultant force needed for an acceleration of 4.0 m/s².
Problem 3 Weight and reaction ★★★
Bilal in Lahore places a 12 kg box on a level table.1. Calculate the weight of the box.
2. Then state the normal reaction on the box.
Problem 4 Sliding crate ★★★
A 25 kg crate slides on a concrete floor in Accra. The coefficient of kinetic friction is 0.30.1. Calculate the normal reaction.
2. Then calculate the friction force.
Problem 5 Pulled box ★★★
A box of mass 8.0 kg is pulled to the right with a force of 60 N. A friction force of 22 N acts to the left.1. Calculate the resultant force.
2. Then calculate the acceleration.
Problem 6 Weight components ★★★
A 4.0 kg block rests on a slope inclined at 25°.1. Calculate the component of weight down the slope.
2. Then calculate the component of weight perpendicular to the slope.
Problem 7 Pushing a crate ★★★
Kofi pushes a 40 kg crate with 180 N across a floor. The coefficient of kinetic friction is 0.35.1. Calculate the friction force.
2. Then calculate the resultant force.
3. Finally, calculate the acceleration.
Problem 8 Moving a bookcase ★★★
Wanjiru’s family in Nairobi move a 15 kg bookcase. μs = 0.45 and μk = 0.32.1. Calculate the force needed to start it moving.
2. Then calculate the friction force once it is sliding.
3. Finally, calculate the acceleration if the push stays at the force in part 1.
Problem 9 Skidding car ★★★
A car skids to a halt from 25 m/s with all wheels locked. Compare dry and wet roads, assuming that the mass of the car does not matter.1. Calculate the deceleration on a dry road with μk = 0.80.
2. Then calculate the skid distance on the dry road.
3. Finally, calculate the skid distance on a wet road with μk = 0.40.
Problem 10 Frictionless sledge ★★★
Mei and a friend slide on a sledge down a smooth icy slope of angle 15° in Canada.1. Calculate the acceleration.
2. Then calculate the speed after the sledge has moved 20 m from rest.
Problem 11 Ramp for a crate ★★★
A 12 kg crate slides down a ramp inclined at 20° with μk = 0.15.1. Calculate the component of weight down the slope.
2. Then calculate the friction force.
3. Finally, calculate the acceleration.
Problem 12 Angle of slipping ★★★
A wooden block begins to slide on a board when the board is tilted to 27°.1. Show that μs = tan θ at the point of slipping.
2. Then calculate μs.
Problem 13 Two blocks pulled ★★★
Diego pulls a 3.0 kg block with a horizontal force of 25 N. It is joined by a rope to a 2.0 kg block behind it. Both rest on a table with μk = 0.20.1. Calculate the total friction force.
2. Then calculate the acceleration of the blocks.
3. Finally, calculate the tension in the rope.
Problem 14 Lift scale reading ★★★
Emma, mass 70 kg, stands on a weighing scale in a lift.1. Calculate the scale reading when the lift accelerates upwards at 1.2 m/s².
2. Then calculate the reading when it accelerates downwards at 1.2 m/s².
3. Finally, calculate the reading at constant velocity.
Problem 15 Spot the slope error ★★★
A student finds the acceleration of an 8.0 kg block sliding down a 35° slope with μk = 0.25. She writes friction f = 0.25 × 8.0 × 9.81 = 19.6 N.1. Explain her mistake.
2. Then calculate the correct friction force and the acceleration.
Problem 16 Trolley and hanging mass ★★★
A 2.0 kg trolley on a rough table (μk = 0.10) is joined by a string over a pulley to a hanging 0.50 kg mass. The system is released from rest.1. Calculate the friction force on the trolley.
2. Then calculate the acceleration of the system.
3. Finally, calculate the tension in the string.
Problem 17 Pushing up a ramp ★★★
Workers push a 20 kg crate up a ramp inclined at 25° with a force parallel to the ramp. μk = 0.30.1. Calculate the force needed for constant speed.
2. Then calculate the acceleration if the push is 180 N.
Problem 18 Friction coefficient from data ★★★
A block is released from rest on a slope inclined at 22°. It slides 1.50 m in 1.10 s.1. Calculate the acceleration of the block.
2. Then show that a = g(sin θ − μ cos θ).
3. Finally, calculate μk.
Problem 19 Car and caravan ★★★
A car of mass 1200 kg tows a caravan of mass 800 kg. The driving force is 3500 N. The resistances are 400 N on the car and 300 N on the caravan.1. Calculate the acceleration.
2. Then calculate the tension in the tow bar.
Problem 20 Crate on a truck ★★★
A 50 kg crate sits on the flat bed of a truck. μs = 0.40 and μk = 0.30 between crate and bed.1. Calculate the greatest acceleration of the truck for which the crate does not slide.
2. The truck accelerates at 4.5 m/s². Calculate the acceleration of the crate.
3. Finally, calculate how far the crate slides back relative to the bed in 2.0 s.
