Can someone solve 42-44. Thank you! A boy throws a ball of mass 025 kg straight
ID: 3278282 • Letter: C
Question
Can someone solve 42-44. Thank you! A boy throws a ball of mass 025 kg straight upward with an initial speed of 20m/s When the ball returns to the boy, its speed is 17m/s How much work does air resistance do on the ball during its flight? A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s Daring its tall, how much work is on the mouse by air resistance? Using energy considerations and assuming negligible air resistance, show that a rock thrown from a bridge 20.0m above water with a initial speed of 15, 0 m/s strikes the water with a speed of 24.8m/s independent of the direction thrown. A 1.0 - kg at the end of a 2.0.m string swings in a vertical plane. At its lowest point the ball is moving with a speed of 10 m/s. (a) what is its speed at the top of its path? (b) What is the tension in the string when the boll at the bottom and at the top of its path? ignoring details associated with frictions, extra forces exerted by arm and leg, muscles, and other factors, we can consider a pole vault as the conversion of an athlete's running kinetic energy to gravitational potential energy. If an athlete is to lift his body 4.8 m during a vault, what speed must behave when he plants his pole? vertically from a tall tree when he is running at 9.0 m/s. (a) how high can be swing upward (b)Does the length of the vine affect this height? Assume that the force of a bow on an arrow behaves like the spring force. In the arrow, an pulls the bow back 50cm and holds it in position with a force of 150N, if the of the arrow is 50g and the "spring" is massless, what is the speed of the arrow after it leaves the bow? A sled of mass 70kg starts from rest and slides down a 10 degree incline 80m long. it then travels for 20m horizontally before starting back up as 8 degree incline. It travels 80m along this incline before coming to rest. What is the net work done on the sled by friction? A girl on a skateboard (total mass of 40kg) is moving at a speed of 10 m/s at the bottom of a long ramp. The ramp is inclined at 20 degree with respect to the horizontal. If she travels 14.2 m upward along the ramp before stopping, what is the net frictional force on her? A baseball of mass 0.25kg is hit at home plate with a speed of 40 m/s. When it lands in a seat in the left-field bleachers a horizontal distance 120m from home place. It is moving at 30 m/s. If the ball lends 20 m above the spot where it was hit, how much work is done on it by air resistance? A small block of mass m slides without friction around the loop-the-loop apparatus shown below. (a) If the block starts from rest at A, what is its speed at B? (b) What is the force of the track on the block at B? The massless spring of a spring gas has a force constant k = 12N/cm. When the gas is aimed vertically, a 15-g projectile is shot a height of 5.0 m above the end of the expanded spring. (See below.) How much was the spring compressed initially? A small ball is tied to a string and set rotating with negligible friction in a vertical circle. Prove that the tension in the string at the bottom of the circle exceeds that at the top of the circle by eight times the weight of the ball. Assume the ball's speed is zero as it fails over the top of the circle and there is no additional energy added to the ball during rotation. A particle of mass 0.50 kg moves along the x-axis with a potential energy whose dependence on x is shown below. (a) What is the force on the particle at x= 2.0, 5.0, 8.0 and 12 m? (b) If the total mechanical energy E of the particle is -6.0 J, what are the minimum and maximum of positions of the particle? (c) What are these positions if E = 20 J? (d) If E = 16 J. What are theExplanation / Answer
Q42. given, mass of block = m
height of A = 4R
Potential energy, PE at A = mgh = mg*4R = 4mgR
this energy gets converted to KE at B as there is no friction
so, PE at B = mgR
KE at B = 0.5mv^2 [ where v is velocity at B]
so, from conservation of mechanical energy
0.5mv^2 + mgR = 4mgR
mv^2 = 6mgR
a. v = sqroot(6gR)
b. force by track = mv^2/R = 6mgR/R = 6mg
Q43. masless spring with spring constant, k = 12 N/cm = 1200 N/m
mass of projectile, m = 0.015 kg
inital compression = x
final height = 5 m
so mgh = 0.5kx^2
x = sqroo(2mgh/k) = sqroot(2*0.015*9.81*5/1200) = 3.507 cm