Newton's Laws

Problems for solution without assistance

Problem 1

If a net horizontal force of 136 N is applied to a person with mass 50 kg who is resting on the edge of a swimming pool, what horizontal acceleration is produced?

Problem 2

A crate with mass 37.5 kg initially at rest on a warehouse floor is acted on by a net horizontal force of 120 N.
a) What acceleration is produced?
b) How far does the crate travel in 10.0 s?
c) What is its speed at the end of 10.0 s?

Problem 3

A hockey puck with mass 0.160 kg is at rest at the origin (x =0) on the horizontal frictionless surface of the rink. At time t =0 a player applies a force of 0.300 N to the puck, parallel to the x-axis; he continues to apply this force until t=2.00 s.
a) What are the position and speed of the puck at t =2.00 s?
b) If the same force is again applied at t=5.00 s, what are the position and speed of the puck at t=7.00 s?

Problem 4

A dockworker applies a constant horizontal force of 90.0 N to a block of ice on a smooth horizontal floor. The frictional force is negligible. The block starts from rest and moves 12.0 m in 5.00 s.
a) What is the mass ofthe block of ice?
b) If the worker stops pushing at the end of 5.00 s, how far does the block move in the next 5.00 s?

Problem 5

At the surface of Mars the acceleration due to gravity is g = 3.72 m/s². A watermelon weighs 52.0 N at the surface of the earth.
a) What is its mass on the earth's surface?
b) What is the mass and weight on the surface of Mars?

Problem 6

Superman throws a 2800-N boulder at an adversary. What horizontal force must Superman apply to the boulder to give it a horizontal acceleration of 15.0 m/s²?

Problem 7

A bowling ball weighs 71.2 N (16.0 lb). The bowlerler applies a horizontal force of 178 N (40.0 lb) to the ball. What is the magnitude of the horizontal acceleration of the ball?

Problem 8

World-class sprinters can accelerate out of the starting blocks with an acceleration that is nearly horizontal and has magnitude 15 m/s². How much horizontal force must a 60-kg sprinter exert on the starting blocks during a start to produce this acceleration? Which body exerts the force that propels the sprinter: the blocks or the sprinter herself?

Problem 9

A student with mass 50 kg jumps off a high diving board. Using 6.0*10²⁴ kg for the mass of the earth, what is the acceleration of the earth toward her as she accelerates toward the earth with an acceleration of 9.8 m/s²? Assume that the net force on the earth is the force of gravity she exerts on it.

Problem 10

An astronaut with mass 95.0 kg is tethered by a strong rope to a space shuttle. The mass of the shuttle is 8.55 * 10⁴ kg, and the mass of the rope can be neglected. The shuttle is far from both the moon and the earth, so we can treat the gravitalional forces on it and the astronaut as negligible. We also assume that both the shuttle and the astronaut are initially at rest in an inertial reference frame, although this is only approximately true. The astronaut then pulls on the rope with a force of 20.0 N.
a) What force does the rope exert on the astronaut?
b) What is the astronaut's acceleration?
c) What force does the rope exert on the shuttle?
d) What is the acceleration of the shuttle?

Problem 11

A 4.80 bucket of water is accelerated upward by a cord of negligible mass whose breaking strength is 60.0 N. Find the maximum upward acceleration that can be given to the bucket without breaking the cord.

Problem 12

A parachutist relies on the drag force of her parachute to reduce her acceleration toward the earth. If she has a mass of 60.0 kg and her parachute drag supplies an upward force of 340 N, what is her acceleration?

Problem 13

Two crates (4 kg and 6 kg) are on a horizontal frictionless surface contacted by a rope of negligable weight. A woman (wearing golf shoes so that she can get traction) applies a horizontal force F = 50.0N to the 6.00-kg crate (by pulling on another rope).
a) Draw a free-body diagram for the 4.00-kg crate, a free body diagram for the 6.00-kg crate, and a free-body diagram for the woman. For each force, indicate what body exerts that force.
b) What is the magnitude of the acceleration of the 6.00-kg crate?
c) What is the tension T in the rope (of negligible mass) connecting the two crates?

Problem 14

An object with mass m moves along the x-axis. Its position as a function of time is given by x(t) = At + Bt³ , where A and B are constants. Calculate the net force on the object as a function of time.

Examples of solutions

back • home • top