Newton's Laws (No Friction/ No Ramps) Page 1a Schaum's 3

1. Newton's Laws (No Friction/ No Ramps) Page 1a Schaum's 3 3.5 A child pulls on a rope attached to a sled with a force of 60N. The rope makes an angle of 400 to the ground. Calculate the x and y components of the force. 3.8 Find the weight on Earth of a body whose mass is a) 300kg b) 200g. 3.9 A 20 kg object that can move freely is subjected to a resultant force of 45N in the -x direction. Find the acceleration of the object. 3.10 A 50N weight is hung by a cord. Find the tension in the cord. 3.11 A 5 kg object is to be given an upward acceleration of 0.30 m/s2 by a rope pulling straight upward on it. What must the tension be? 3.13 The only force acting on a 5 kg object has components Fx = 20 N and Fy = 30 N. Find the acceleration of the object. 3.14 A 600 N object is to be given an acceleration of 0.7 m/s2. How large an unbalanced force must act upon it? 3.15 A constant force acts on a 5 kg object and reduces its velocity from 7 m/s to 3 m/s in a time of 3 seconds. Find the force.

2. Newton's Laws (No Friction/ No Ramps) Page 1b Schaum's 3 3.18 An 8000 kg engine pulls a 40,000kg train along a level track and gives it an acceleration a1 = 1.2 m/s2. What acceleration (a2) would the engine give to a 16,000 kg train? 3.19 As shown in Figure I, an object of mass m is supported by a cord. Find the tension in the cord if the object is a) at rest b) moving at constant velocity c) accelerating upward with acceleration a = 3g/2 and downward at a= .75g. m 3.20 A tow rope will break if the tension in it exceeds 1500 N. It is used to tow a 700 kg car along level ground. What is the largest acceleration the rope can give to the car? 3.21 Compute the least acceleration with which a 45 kg woman can slide down a rope if the rope can withstand a tension of only 300 N. 3.30 A cord passing over a massless and frictionless pulley has a 7 kg mass hanging from one end and a 9 kg mass hanging from the other (Atwood's machine). Find the acceleration of the masses and the tension in the cord.

3. Newton's Laws (No Friction/ No Ramps) Page 1c Schaum's 3 3.47 A force acts on a 2 kg mass and gives it an acceleration of 3 m/s2. What acceleration is produced by the same force when it is acting on a mass of a) 1 kg b) 4 kg 3.48 An object has a mass of 300 g. a) What is its weight on earth? b) What is its mass on the moon? c) What will be its acceleration on the Moon when a 0.500 N resultant force acts on it? 3.49 A horizontal cable pulls a 200 kg cart along a horizontal track. The tension in the cable is 500 N. Starting from rest a) How long will it take the cart to reach a speed of 8 m/s? b) How far will it have gone? 3.50 A 900 kg car is going 20 m/s along a level road. How large a constant retarding force is required to stop it in a distance of 30 m? 3.51 A 12 g bullet is accelerated from rest to a speed of 700 m/s as it travels 20 cm in a gun barrel. How large was the accelerating force? 3.52 A 20 kg crate hangs at the end of a long rope. Find its acceleration (include direction) when the tension in the rope is a) 250 N b) 150 N c) 0 d) 196 N 3.53 A 5 kg mass hangs at the end of a cord. Find the tension in the cord if the acceleration of the mass is a) 1.5 m/s2 up b) 1.5 m/s2 down c) 9.8 m/s2 down

4. Newton's Laws (No Friction/ No Ramps) Page 1d Schaum's 3 3.54 A 700 N man stands on a scale on the floor of an elevator. The scale records the force it exerts on whatever is on it. What is the scale reading if the elevator has an acceleration of a) 1.8 m/s2 up b) 1.8 m/s2 down c) 9.8 m/s2 down 3.55 Using the scale described in 3.54, a 65 kg astronaut weighs himself on the Moon, where g = 1.6 m/s2. What does the scale read? 3.56 A cord passing over a frictionless, massless pulley has a 4 kg object tied to one end and a 12 kg object tied to the other. Compute the tension and acceleration in the cord. 3.57 An elevator starts from rest with a constant upward acceleration. It moves 2 m in the first 0.6 s. A passenger in the elevator is holding a 3 kg package by a vertical string. What is the tension in the string during acceleration? 3.58 Just as her parachute opens, a 60 kg parachutist is falling at a speed of 50 m/s. After 0.80 s has passed, the chute is fully open and her speed has dropped to 12 m/s. Find the average retarding force exerted upon the chutist during this time if the deceleration is uniform. 3.59 A 300 mg mass hangs at the end of a string. A second string hangs from the bottom of that mass and supports a 900 g mass. Find the tension in each string when the masses are accelerating a) upward 0.7 m/s2 a) down 0.7 m/s2