You stand on a hill. What force prevents you from sliding down the hill? a)  Gravity b)  Normal Force c)  Inertia d)  Kinetic Friction e)  Static Friction

A box is at rest with respect to the surface of a flatbed truck. The coefficient of static friction between the box and the surface is s. a. Find an expression for the maximum acceleration of the truck so that the box remains at rest with respect to the truck. Your expression should be in terms of s and g. b. How does your answer change if the mass of the box is doubled?

A man exerts a force of 16.7 N horizontally on a box so that it is at rest in contact with a wall as in Figure 6.3. The box weighs 6.52 N. a. Find the static friction force exerted on the box, given the forces being applied, b. If the coefficient of static friction between the wall and the box is 0.50, find the maximum static friction force that may be exerted on the box. Comment on your results.

The distance between two telephone poles is 50.0 m. When a 1.00-kg bird lands on the telephone wire midway between the poles, the wire sags 0.200 m. (a) Draw a free-body diagram of the bird. (b) How much tension does the bird produce in the wire? Ignore the weight of the wire.

Friction The glue on a piece of tape can exert forces. Can these forces be a type of simple friction? Explain, considering especially that tape can stick to vertical walls and even to ceilings.

A person holds a ball in her hand. (a) Identify all the external forces acting on the ball and the Newtons third-law reaction force to each one. (b) If the ball is dropped, what force is exerted on it while it is falling? Identify the reaction force in this case. (Ignore air resistance.)

A horse is harnessed to a sled having a mass of 236 kg, including supplies. The horse must exert a force exceeding 1 240 N at an angle of 35.0 in order to get the sled moving. Treat the sled as a point particle, (a) Calculate the normal force on the sled when the magnitude of the applied force is 1 240 N. (b) Find the coefficient of static friction between the sled and the ground beneath it. (c) Find the static friction force when the horse is exerting a force of 6.20 102 N on the sled at the same angle.

Forensic Science Forensic science is the application of scientific techniques and methodology to discover the cause of a particular event such as an accident. Modern forensics have been used to solve historic crimes and mysteries such as the cause of death of King Tutankhamen of ancient Egypt and composer Ludwig van Beethoven in 1827. Forensic evidence is often admitted into a court case. For example, skid marks at an accident scene are used to find the initial speed of a car. Explain why skid marks are left by the car and how they may be used to find the cars initial speed.

A 1.00 103 car is pulling a 300.-kg trailer. Together, the car and trailer have an acceleration of 2.15 m/s2 in the positive x-direction. Neglecting frictional forces on the trailer, determine (a) the net force on the car, (b) the net force on the trailer, (c) the magnitude and direction of the force exerted by the trailer on the car, and (d) the resultant force exerted by the car on the road.

Review. A rifle bullet with a mass of 12.0 g traveling toward the right at 260 m/s strikes a large hag of sand and penetrates it to a depth of 23.0 cm. Determine the magnitude and direction of the friction force (assumed constant) that acts on the bullet.