A chair of mass 10kg is sitting on a horizontal floor which is not frictionless. You push on the chair with a constant force of magnitude 30 N which is directed at an angle of 30° below the horizontal and chair sides along the floor. Draw free-body diagram and calculate the normal force that the floor exerts on the chair.
Ans: 115 N
An iron block of mass 10 kg rests on a wooden plane inclined at 30° to the horizontal. It is found that the least force parallel to the plane which causes the block to slide up is 100 N. Calculate the coefficient of friction between two surfaces.
Ans: 0.577
A box of mass 15 kg placed on horizontal floor is pulled by a horizontal force. What will be the work done by the force if the coefficient of sliding friction between the box and the surface of the floor is 0.3 and body moved at unit distance?
Ans: 45 J
A little red wagon with mass 7 kg moves in a straight line on a frictionless horizontal surface. It has an initial speed of 4m/s and then is pushed 3 m in the direction of the initial velocity by a force of 10N. Calculate the wagon's final speed and the acceleration produced by the force.
Ans: 4.96m/sec, 1.43 m/sec2
In a physics lab experiment, a 6kg box is pushed across a flat table by a horizontal force F.
Ans: (i) 7.2 N (ii) 8.28 N
A 550N physics student stands on a bathroom scale in an elevator. As the elevator starts moving the scale reads 450N. Draw free-body diagram of the problem and find the magnitude and direction of the acceleration of the elevator.
Ans: 1.8 m/sec2
A ball of mass 0.05Kg strikes a smooth wall normally four times in 2 seconds with a velocity of 10ms-1. Each time the ball rebounds with the same speed of 10ms-1. Calculate the average force on the wall.
Ans: 2 N
A cricket ball of mass 145 g is moving with a velocity of 14m/s and is being hit by a bat, so that the ball is turned back with a velocity of 22m/s. The force of blow acts on the ball for 0.015 sec. Find the average force exerted. by the bat on the ball.
Ans: 348 N
What would be the acceleration of a block sliding down an inclined plane that makes an angle of 45° with the horizontal if the coefficient of sliding friction between two surfaces is 0.3?
Ans: 4.95 m/sec2
In a physics lab experiment, a 6kg box is pushed across a flat table by a horizontal force F. If the box is moving at a constant speed of 0.35m/s and the coefficient of kinetic friction is 0.12, find the magnitude of force F. What is the magnitude of force F if the box is moving with a constant acceleration of 0.18 m/s2?
Ans: 7.2 N, 8.28 N
A light rope is attached to a block with mass 4 kg that rests on a frictionless, horizontal surface. The horizontal rope passes over a frictionless pulley and a block with mass m is suspended from the other end. When the blocks are released, the tension in the rope is 10 N. Draw free body diagrams and calculate the acceleration of either block and the mass m of the hanging block.
Ans: 2.5 m/sec2, 1.33 kg
Two masses 7 kg and 12 kg are connected at the two ends of a light inextensible string that passes over a frictional pulley. Using free body diagram method, find the acceleration of masses and the tension in the siring, when the masses are released.
Ans: 2.63 m/sec2; 88.42 N
A 15 kg load of bricks hangs from one end of a rope that passes over a small, frictionless pulley. A 28 kg counterweight is suspended from the other end of the rope as shown in the figure. The system is released from rest. Using free body diagram method, find the magnitude of upward acceleration of the load and the tension in the rope while the load is moving.
Ans: 3.02/sec2 and 195.35 N
Suppose you try to move a crate by tying a rope around it and pulling on the rope at an angle of 30° above the horizontal. What is the tension required to keep the crate moving with constant velocity? Assume weight of the crate 'w' = 500 N and coefficient of dynamic friction μk = 0.40
Ans: 187.6 N
