2. A of 3 m/s sied, whose mass is 12 kg is moving along the horizontal with an o
ID: 1795381 • Letter: 2
Question
2. A of 3 m/s sied, whose mass is 12 kg is moving along the horizontal with an original velocity s passes over a rough patch in the snow of 0.8 m in length. If the force of cion between the ground and the sled is -14 Nt determine: (a) Keoi (b) work done by friction; (c) Vor of the sled. A block whose mass, m 25 kg, is initially at rest on the horizontal. if a 100 Nt force 3. is applied to the mass parallel to the horizontal and displaces the mass a distance of 12 m det assuming no friction. 4. A toy rocket of mass 0.459 kg is launched upward with a velocity of 18.5 m/s. Determine the height to which the rocket rises. Write in words Newton's three Laws of Motion. A person standing on the roof of a 12 m high building throws a ball upward at 22 m/s Determine: (a) how high the ball goes with respect to the ground and (b) the ball's velocity at impact with the ground. (Hint: Use The Law of Conservation of Energy).Explanation / Answer
2.
a)
Coefficient of kinetic friction = Frictional force / mg
= 14 / [12 x 9.8]
= 0.12
b)
Work done by friction = Frictional force x distance
= 14 x 0.8 = 11.2 J
c)
Deceleration due to frictional force = Frictional force / mass
= 14/12 = - 1.67 m/s2.
Initial velocity = 3 m/s
Distance traveled, s = 0.8 m
Using the formula, v2 - u2 = 2as,
v2 = u2+ 2as
= 9 + 2 x (- 1.67) x 0.8 = 7.133
v = SQRT[7.133]
= 2.67 m/s
3.
a)
Work done = Force x distance
= 100 x 12
= 1200 J
b)
Acceleration = Force / mass
= 100 / 25 = 4 m/s2.
Initial velocity, u = 0
Distance travelled, s = 12 m
Take the final velocity as v
Using the equation v2 - u2 = 2as,
v2 = u2 + 2as
= 0 + 2 x 4 x 12 = 96
v = SQRT[96]
= 9.8 m/s
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