2. The 2 kg book is held 1 m above the floor for 50 s. The work done is (W = mgh

Question

2. The 2 kg book is held 1 m above the floor for 50 s. The work done is (W = mgh, g = 9.8ms2)

Question 2 options:

0 J

10.2 J

100 J

980 J

3. A 3000-kg truck accelerates from 10 m/s to 30 m/s in 8 s. The net force on the truck is (F = mass x acceleration, acceleration = vfinal - vinitial/time, F = mass x vfinal - vinitial/time)

Question 3 options:

765 N.

7500 N.

11,250 N

15,000 N.

4. The linear momentum of a 400 kg horse galloping at 5 m/s is (linear momentum = mass x velocity)

Question 4 options:

80 kg . m/s

2000 kg . m/s

5000 kg . m/s

19,600 kg . m/s

5. Work = mxgxh and g = 9.8 ms2. The work done in lifting 30 kg of bricks to a height of 20 m on a building under construction is

Question 5 options:

61 J

600 J

2940 J

5880 J

6. A car starts from rest and reaches a speed of 12 m/s in 20 s. Its acceleration is

{(Vfinal - Vinitial)/t = acceleration}

Question 6 options:

0.6 m/s2.

4 m/s2.

6 m/s2.

240 m/s2.

7. A 1-kg mass has a KE of 1 J when its speed is (KE = (1/2) mv2)

Question 7 options:

0.45 m/s

1 m/s

1.4 m/s

4.4 m/s

8. A 1000 kg car whose speed is 22.2 m/s has a kinetic energy of (KE = (1/2) x m v2)

Question 8 options:

25.2 X 103 J

24.6 X 104 J

2.42 X 106 J

3.2 X 106 J

9. Kinetic energy may be thought of as the energy of motion

Question 9 options:

False

10. The mass of a sack of potatoes whose weight is 200 N is (W = m.g and g = 9.8 m/s2)

Question 10 options:

20.4 kg.

91 kg.

210 kg.

440 kg.

0 J

10.2 J

100 J

980 J

3. A 3000-kg truck accelerates from 10 m/s to 30 m/s in 8 s. The net force on the truck is (F = mass x acceleration, acceleration = vfinal - vinitial/time, F = mass x vfinal - vinitial/time)

Question 3 options:

765 N.

7500 N.

11,250 N

15,000 N.

4. The linear momentum of a 400 kg horse galloping at 5 m/s is (linear momentum = mass x velocity)

Question 4 options:

80 kg . m/s

2000 kg . m/s

5000 kg . m/s

19,600 kg . m/s

5. Work = mxgxh and g = 9.8 ms2. The work done in lifting 30 kg of bricks to a height of 20 m on a building under construction is

Question 5 options:

61 J

600 J

2940 J

5880 J

6. A car starts from rest and reaches a speed of 12 m/s in 20 s. Its acceleration is

{(Vfinal - Vinitial)/t = acceleration}

Question 6 options:

0.6 m/s2.

4 m/s2.

6 m/s2.

240 m/s2.

7. A 1-kg mass has a KE of 1 J when its speed is (KE = (1/2) mv2)

Question 7 options:

0.45 m/s

1 m/s

1.4 m/s

4.4 m/s

8. A 1000 kg car whose speed is 22.2 m/s has a kinetic energy of (KE = (1/2) x m v2)

Question 8 options:

25.2 X 103 J

24.6 X 104 J

2.42 X 106 J

3.2 X 106 J

9. Kinetic energy may be thought of as the energy of motion

Question 9 options:

True

False

10. The mass of a sack of potatoes whose weight is 200 N is (W = m.g and g = 9.8 m/s2)

Question 10 options:

20.4 kg.

91 kg.

210 kg.

440 kg.

Explanation / Answer

2. As work done is W = mgh , but book is held not moved hence, height covered = 0.

Hence, work W = 0 J

3. As force F = m (v2 - v1)/t = 3000 x (30-10)/8 = 7500 N

4. Momentum = mass x velocity = 400 x 5 = 2000 kgm/s

5. Work done in moving 30 kgbricks to 20 m height is

W = mgh = 30 x 9.8 x 20 = 5880 J

6. Acceleration a = (12-0)/20= 12/20 = 0.6 m/s2

7. As KE = 1 J, mass = 1 kg

1/2 mv2= 1

1/2 x 1 x v2 = 1

v = (2)1/2 = 1.414 m/s

8. KE = 1/2 mv2 = 1/2 x 1000 x 22.22 = 24.6 x 104 J

9. Weight = mg

m = 200/9.8 = 20.4 kg

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