Conservation of energy Knowledge-Based Download PDF

Questions

1. 1.

   A parachutist of mass 60 kg descends vertically at a constant speed of 10 m/s. Taking the acceleration due to gravity as $10\text{ m/s}^2$, how much thermal energy is transferred to the surroundings due to air resistance as the parachutist falls through a vertical distance of 40 m?

   • A) 21 kJ
   • B) 24 kJ
   • C) 27 kJ
   • D) 3.0 kJ
2. 2.

   A 1.0 kg block is dropped from rest from a height of 0.80 m above an uncompressed vertical spring and momentarily stops after compressing it by 0.20 m. Neglecting air resistance and taking the acceleration due to gravity as $10\text{ m/s}^2$, what is the spring constant of the spring?

   • A) 400 N/m
   • B) 500 N/m
   • C) 250 N/m
   • D) 100 N/m
3. 3.

   A 0.20 kg ball is dropped from rest from a height of 5.0 m above a flat floor and bounces vertically upward to a maximum height of 3.2 m. Taking the acceleration due to gravity as 10 m/s², how much mechanical energy is converted into other forms of energy during the bounce?

   • A) 1.8 J
   • B) 6.4 J
   • C) 10.0 J
   • D) 3.6 J
4. 4.

   A vertical spring launcher stores 18 J of elastic potential energy when compressed. Neglecting air resistance and taking the acceleration due to gravity as 10 m/s², what maximum height above its release point does a 0.15 kg projectile reach when launched vertically upward?

   • A) 4.5 m
   • B) 6.0 m
   • C) 9.0 m
   • D) 12 m
5. 5.

   A 0.50 kg ball is thrown vertically upward from ground level with an initial speed of 20 m/s. Neglecting air resistance, what is the total mechanical energy of the ball relative to the ground when it reaches half of its maximum height?

   • A) 100 J
   • B) 50 J
   • C) 75 J
   • D) 25 J
6. 6.

   An object is released from rest from a height $H$ above the ground. Neglecting air resistance and taking the ground as the reference level, at what height above the ground is the kinetic energy of the object three times its gravitational potential energy?

   • A) $\frac{3}{4}H$
   • B) $\frac{1}{3}H$
   • C) $\frac{1}{4}H$
   • D) $\frac{2}{3}H$
7. 7.

   A small block slides down a frictionless curved ramp from a height of 0.80 m above the ground with an initial speed of 3.0 m/s. Neglecting air resistance and taking the acceleration due to gravity as $10\text{ m/s}^2$, what is the speed of the block as it reaches the ground?

   • A) 4.0 m/s
   • B) 4.1 m/s
   • C) 7.0 m/s
   • D) 5.0 m/s
8. 8.

   A cart with an initial kinetic energy of 80 J moves up an inclined track until it momentarily comes to rest at its highest point. If friction generates 30 J of thermal energy during the climb, what is the gravitational potential energy of the cart at this highest point?

   • A) 110 J
   • B) 80 J
   • C) 50 J
   • D) 30 J
9. 9.

   A horizontal spring with a spring constant of 200 N/m is compressed by 0.20 m against a 0.50 kg block resting on a frictionless surface. When the spring is released, all of its stored elastic potential energy is converted into the kinetic energy of the block. What is the speed of the block as it leaves the spring?

   • A) 1.6 m/s
   • B) 2.0 m/s
   • C) 4.0 m/s
   • D) 16 m/s
10. 10.

    A 4.0 kg object is released from rest from a height of 15 m above the ground where air resistance is negligible. Taking the acceleration due to gravity as $10\text{ m/s}^2$, what is the kinetic energy of the object when it reaches a height of 5.0 m above the ground?

    • A) 200 J
    • B) 300 J
    • C) 400 J
    • D) 600 J